Bernhard Lauterburg - Academia.edu (original) (raw)
Papers by Bernhard Lauterburg
Gastroenterology 90(5 Part, Sep 2, 1986
Therapeutische Umschau. Revue thérapeutique, 1987
The Journal of laboratory and clinical medicine, 1979
Removal of protein-bound cholephilic substances such as BA by sorbent perfusion might improve the... more Removal of protein-bound cholephilic substances such as BA by sorbent perfusion might improve the quality of life of patients with severe inoperable cholestasis where the accumulation of BA is thought to be responsible for the often distressing pruritus. Since hemoperfusion is associated with hematological side effects, plasmaperfusion which, in addition, allows the use of novel, possibly more efficient sorbents, might be preferable, provided a substance with a high affinity for these protein-bound anions could be found. A number of sorbents suitable for plasma-perfusion were therefore tested in vitro as to their BA-adsorbing capacity. U.S.P. charcoal coated onto glass beads in order to facilitate perfusion removed BA from human plasma far better than conventional charcoal suitable for hemoperfusion, charged and uncharged resins, and immobilized albumin. The extraction of BA by the coated glass beads exceeded 90% up to a load of 0.18 mumol BA per milliliter of sorbent, and the BA-ad...
The International Journal of Artificial Organs, 1980
Patients with severe, inoperable cholestasis and intractable pruritus not responding to conventio... more Patients with severe, inoperable cholestasis and intractable pruritus not responding to conventional medical therapy might benefit from a depletion of their bile acid pool by sorbent perfusion since accumulated bile acids are possibly responsible for their itching. In vitro, USP-charcoal-coated glass beads removed bile acids from human plasma far better than any other sorbent tested. In order to demonstrate the safety and efficacy of charcoal plasmaperfusion in vivo, five dogs underwent plasmapheresis one week following cholecystectomy and bile duct ligation, and 2.2 ± 0.2 (x̄ ± SD) times their plasma volume was passed over a column containing 400 ml of charcoal-coated glass beads prior to reinfusion. During the procedure the plasma bile acid concentration was reduced by 40.2 ± 4.0% and the bilirubin level by 48.2 ± 3.3%. The columns, whose capacity was far from being saturated, retained 1.3 ± 0.4 times the pre-perfusion plasma pool of bile acids (1.1 ± 0.2 for bilirubin) suggesting...
Journal of Hepatology, 2005
PubMed, Apr 25, 1992
Excessive consumption of ethanol results in reversible redox changes in the liver that are mainly... more Excessive consumption of ethanol results in reversible redox changes in the liver that are mainly responsible for the accumulation of triglycerides and the fatty liver of the alcoholic patient. In spite of continuing alcohol abuse, only a fraction of all alcoholics will develop alcoholic hepatitis and eventually cirrhosis. Genetic predisposition and environmental factors (in particular the often poor nutrition of the alcoholic) probably play an important role in the evolution of these complications. The generation of reactive oxygen species increases during the metabolism of ethanol, but their pathogenetic role in alcoholic liver disease in man is not clear. Acetaldehyde, a metabolite of ethanol, can react with proteins and form stable adducts. Such neoantigens may elicit an immunologic response which could in part be responsible for the liver cell damage associated with excessive alcohol consumption. Since no satisfactory animal model for alcoholic liver disease exists, the relative importance of the various factors involved in alcoholic liver disease is difficult to assess.
PubMed, Feb 1, 1998
Only about 15% of the subjects abusing ethanol will eventually develop cirrhosis of the liver, su... more Only about 15% of the subjects abusing ethanol will eventually develop cirrhosis of the liver, suggesting that other factors in addition to the consumption of large quantities of ethanol play a role in the pathogenesis of alcoholic cirrhosis. Important contributors may be infection with hepatitis viruses, in particular HCV, protein-calorie malnutrition and immunologic factors. Abstinence improves the prognosis of patients with alcoholic cirrhosis, provided that the liver disease is not too far advanced. No pharmacotherapeutic intervention has shown a convincing improvement of the prognosis of alcoholic liver disease, so that the therapeutic efforts should be mainly directed towards abstinence. The patient with alcoholic liver disease needs support and guidance by the treating physicians. Supportive treatment with Disulfiram, Acamprosate or Naltrexon can help with achieving durable abstinence.
PubMed, Sep 21, 1985
Metabolism of drugs by the drug-metabolizing enzyme system usually results in the formation of le... more Metabolism of drugs by the drug-metabolizing enzyme system usually results in the formation of less toxic substances that are readily excreted. A major advance in toxicology, however, has been the observation that the same enzyme system can also activate innocuous drugs into reactive and highly toxic metabolites. Depending on their chemical nature, these metabolites either covalently bind to cellular macromolecules, give rise to toxic oxygen species, or react with membrane lipids to form lipid peroxides. Glutathione, vitamin E and possibly other antioxidants play an important role in protecting the cell from these toxic species. Alteration of a cellular protein by a chemically reactive metabolite may lead to the formation of an antigen and result in an allergic reaction with not only hepatic, but also systemic, manifestations. The formation of toxic metabolites has been postulated in the hepatotoxicity of acetaminophen, isoniazid, halothane, erythromycin and valproic acid. With other drugs, altered pharmacokinetics in the poor metabolizer phenotype and elderly patients may predispose to toxic reactions.
PubMed, Jul 1, 1977
Because of the discovery of uric acid urolithiasis in rats after end-to-side portacaval anastomos... more Because of the discovery of uric acid urolithiasis in rats after end-to-side portacaval anastomosis (PCA), uric acid metabolism was studied in these animals and in appropriate controls. Hyperuricemia and hyperuricosuria were observed in all experimental rats. The fraction of purine catabolites excreted in the urine as uric acid increased from an average of 4.8% to 15.3%. If 14C-uric specifically labeled at position 6 (6-14C-ua) was infused intravenously and the exhalation of 14CO2 was used to calculate a hepatic uric acid clearance, it decreased from 2.14 to 0.97 ml/min/100 gm despite a normal content of hepatic uricase activity as measured in liver homogenates. The fraction of the filtered amount of uric acid excreted in the urine increased from an average of 11% to 30%. Increased supersaturation of the urine with uric acid after PCA may be expected to contribute to the formation of uric acid urolithiasis. This investigation defines a hepatic and renal functional defect in uric acid metabolism which occurs as a result of the PCA.
PubMed, Jul 1, 1984
Ethanol-induced depletion of hepatic glutathione has been construed as evidence supporting the hy... more Ethanol-induced depletion of hepatic glutathione has been construed as evidence supporting the hypothesis that reactive oxygen intermediates generated during the metabolism of ethanol lead to glutathione oxidation and lipid peroxidation and are responsible for the toxic effects of ethanol. However, the evidence for a pathogenetic role of lipid peroxidation in ethanol-induced liver injury is indirect and a decreased synthesis might well account for the glutathione depletion produced by large doses of ethanol. In order to determine whether a decreased synthesis or an increased consumption of glutathione is responsible for the ethanol-induced glutathione depletion, hepatic glutathione turnover, plasma glutathione and the biliary excretion of glutathione and its disulfide were measured in rats. The administration of 5 g/kg of ethanol p.o. resulted in a decreased incorporation of labeled cysteine and labeled methionine into the hepatic glutathione pool and decreased the hepatic concentration of glutathione from 3.7 +/- 0.1 to 2.7 +/- 0.2 mumol/g. Kinetic analysis of the specific activity-time curves revealed that ethanol decreased significantly the rate of influx of cysteine into the glutathione pool but did not stimulate the rate of consumption of glutathione. Moreover, the plasma concentration of glutathione and the biliary excretion of glutathione disulfide and reduced glutathione decreased after the administration of ethanol, indicating that ethanol does not increase the efflux of glutathione from the liver. Our data demonstrate that a large dose of ethanol does not produce an oxidative stress, which would increase glutathione consumption, but rather impairs glutathione synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)
Journal of Applied Physiology, Jul 1, 1988
Endotoxin-induced oxidative stress is investigated in rats by measuring changes in plasma and lun... more Endotoxin-induced oxidative stress is investigated in rats by measuring changes in plasma and lung tissue levels of glutathione disulfide (GSSG) using a modified enzymatic assay that allows simultaneous measurement of up to 80 samples. Salmonella enteritidis endotoxin (2 and 20 mg/kg) acutely increased both plasma reduced glutathione and GSSG with a rise in the ratio of GSSG to total glutathione. This increase in GSSG was enhanced by pretreatment with 1,3-bis(2-chloroethyl)1-nitrosourea (BCNU), an inhibitor of the glutathione reductase enzyme. However, there was no significant arteriovenous difference in plasma GSSG across the lung, and lung tissue GSSG did not increase after endotoxin treatment. The increase in plasma GSSG was not blocked by vinblastine-induced neutropenia and could not be reproduced by incubating rat blood in vitro with endotoxin. Receptor antagonists of platelet-activating factor (PAF), at a dose that previously inhibited endotoxin-induced lung injury, attenuated the endotoxin-induced increase in plasma GSSG. We conclude that endotoxin causes neutrophil-independent oxidative stress in rats, which may be enhanced by the action of platelet-activating factor.
PubMed, Dec 1, 1985
The plasma concentrations of isoniazid and its hydrazino metabolites, acetylisoniazid, acetylhydr... more The plasma concentrations of isoniazid and its hydrazino metabolites, acetylisoniazid, acetylhydrazine and diacetylhydrazine, were measured by gas chromatography-mass spectrometry in 12 healthy subjects after the ingestion of 300 mg of isoniazid. The area under the plasma concentration-time curve of acetylisoniazid and diacetylhydrazine increased with increasing rate of acetylation of isoniazid. In contrast, the area under the plasma concentration-time curve of acetylhydrazine, the postulated precursor of a toxic metabolite formed from isoniazid, was greater in slow acetylators. This occurred even though rapid acetylators generated more acetylisoniazid and thus more acetylhydrazine from isoniazid, because the rapid acetylators also acetylated acetylhydrazine faster to diacetylhydrazine than did the slow acetylators. Due to this complex relationship between area under the plasma concentration-time curve of acetylhydrazine and the rate of isoniazid acetylation (i.e., a faster rate of formation of acetylhydrazine is accompanied by a faster clearance to diacetylhydrazine), the rate of acetylation of isoniazid minimally influences the exposure of most patients to acetylhydrazine. This pharmacokinetic analysis, however, also shows that the apparent plasma half-life of acetylhydrazine is about five times longer than the plasma half-life of isoniazid, and thus repeated doses of isoniazid should lead to an accumulation of acetylhydrazine in the slowest acetylators in which the plasma half-life of acetylhydrazine is 20-plus hr.(ABSTRACT TRUNCATED AT 250 WORDS)
PubMed, Apr 1, 1991
L-2-oxothiazolidine-4-carboxylic acid (OTC), a prodrug of cysteine, was administered at a dose of... more L-2-oxothiazolidine-4-carboxylic acid (OTC), a prodrug of cysteine, was administered at a dose of 0.15 and 0.45 mmol/kg to healthy volunteers. The plasma concentration of OTC reached a peak between 45 and 60 min after p.o. administration. The p.o. clearance of 0.15 mmol/kg of OTC was 0.57 +/- 0.20 liters/(hr.kg) S.D.. The peak increase in plasma OTC was followed by an increase in the plasma concentration of cysteine which rose by 18 to 75 microM over the average basal concentration of 17 microM. The plasma concentrations of free glutathione and total glutathione (i.e., glutathione in small molecular and protein mixed disulfides) did not change significantly during 8 hr after the ingestion of OTC. In contrast, there was a significant increase in the average concentration of cysteine from 0.37 to 0.99 nmol/mg of protein and of glutathione from 8.7 to 15.6 nmol/mg of protein in lymphocytes 2 to 3 hr after ingestion of OTC. The present data shows that OTC is a prodrug of cysteine after p.o. administration in humans and that OTC can raise the circulating concentration of cysteine and the intracellular concentration of cysteine and glutathione in lymphocytes.
PubMed, Oct 1, 1985
Although diquat produces massive oxidant stress in both Fischer and Sprague-Dawley rats, the Fisc... more Although diquat produces massive oxidant stress in both Fischer and Sprague-Dawley rats, the Fischer rats sustain hepatic necrosis and the Sprague-Dawley rats do not. A previous example of probable hepatic necrosis produced by an oxidant stress-generating compound was demonstrated in animals in which glutathione peroxidase activity had been decreased by a dietary deficiency of selenium. In the present study the susceptible Fischer rats had hepatic peroxidase activities equal to the resistant Sprague-Dawley rats. Hepatotoxic doses of diquat did not diminish hepatic glutathione peroxidase or reductase activities or hepatic content of ascorbic acid, NADPH or protein sulfhydryls. Hepatic nonprotein sulfhydryls were decreased by 50% but recovered to control values by 6 h. Biliary excretion of oxidized glutathione in the Fischer rat after administration of diquat was 4 times that observed after administration in Sprague-Dawley rats. The diquat-induced peroxidation of hepatic lipids was indicated by small increases in the 11-, 12-, and 15-hydroxyeicosatetraenoic acids, as quantitated by a new gas chromatography-mass spectrometry assay. Thus, acute lethal injury caused by redox cycling compounds that generate reactive oxygen species does not exhibit a number of the biochemical alterations in vivo that occur with cell death produced by similar compounds in isolated hepatocyte systems.
PubMed, Apr 1, 1980
We have validated a method to assess hepatic glutathione turnover in individual animals in vivo. ... more We have validated a method to assess hepatic glutathione turnover in individual animals in vivo. This method would be applicable to man by collection of bile samples via nasoduodenal intubation. The rate of glutathione turnover was calculated from the time course of the specific activity of the glutathione-acetaminophen adduct in bile after the administration of a radiolabeled glutathione precursor and a small dose of acetaminophen. Identical results were obtained with radiolabeled glutathione or with radiolabeled cysteine, glutamic acid or glycine as the precursors. The small dose of acetaminophen administered to trap glutathione as an excretable adduct did not stimulate glutathione turnover, which reflects glutathione synthesis under steady-state conditions. No evidence for two pools of glutathione with different half-lives was found; previous reports of two glutathione pools may have failed to account for hepatic protein turnover with subsequent release of radiolabeled amino acids for glutathione synthesis. In male rats, the rate of glutathione turnover decreased from 0.52 per hr at 6 weeks of age to 0.12 per hr at 24 weeks of age. After acute depletion of glutathione by diethylmaleate, the rate of glutathione turnover promptly doubled in all age groups. Similar increases in the rate of glutathione synthesis and in the ability to stimulate glutathione production in response to acute depletion in children might explain their decreased susceptibility to acetaminophen hepatotoxicity.
PubMed, Feb 1, 1976
Current in vivo methods do not give information about the drug-metabolizing capacity (Vmax) and t... more Current in vivo methods do not give information about the drug-metabolizing capacity (Vmax) and the affinity of the microsomal enzyme system for the drug i.e., the dose yielding Vmax/2 (Kd). To explore the possibility of estimating these variables from demethylation rates measured by 14CO2 exhalation, various doses of 14C-aminopyrine were injected i.v. to unanesthetized rats. Drug clearances based on 14CO2 exhalation agreed well with those derived from plasma disappearance rates. Evaluation of dose-response curves revealed saturation phenomena. In the normal rat, a Vmax of 173 nmol/min/100 g and Kd of 26 mumol/100 g could be calculated. Enzyme induction with phenobarbital increased Vmax to 745 nmol/min/100 g, whereas in the rat with portacaval shunt, it was reduced to 45 nmol/min/100 g. After 48-hour bile duct ligation, Vmax was not significantly different from the controls, but Kd increased to 36 mumol/100 g compatible with a competitive type of inhibition of aminopyrine demethylation. Two-thirds hepatectomy reduced Vmax by only 50% suggesting that a substantial portion of demethylation occurs extrahepatically. The approach presented appears to be a valid alternative to conventional plasma clearance methods allowing interpretation of some mechanisms affecting in vivo drug metabolism under various conditions.
European Journal of Clinical Investigation, Feb 1, 1991
Parenteral glutathione has therapeutic potential for targeted delivery of cysteine equivalents. T... more Parenteral glutathione has therapeutic potential for targeted delivery of cysteine equivalents. Thus, high doses of reduced glutathione (GSH) protect from the nephrotoxic and urotoxic effects of cisplatinum and oxazaphosphorines. In order to elucidate the underlying mechanisms the kinetics and the effect of glutathione on plasma and urine sulphydryls were studied in 10 healthy volunteers. Following the intravenous infusion of 2 g m-* of glutathione the concentration of total glutathione in plasma increased from 17.5 k 13.4 pmol 1-' (mean+SD) to 823rt326 pmol I-'. The volume of distribution of exogenous glutathione was 176 k 107 ml kg-and the elimination rate constant was 0.063 k0.027 min-' corresponding to a half-life of 14.1 k9.2 min. Cysteine in plasma increased from 8.9 & 3.5 pmol I-' to 114k45 pmol I-' after the infusion. In spite of the increase in cysteine, the plasma concentration of total cyst(e)ine (i.e. cysteine, cystine, and mixed disulphides) decreased, suggesting an increased uptake of cysteine from plasma into cells. Urinary excretion of glutathione and of cyst(e)ine was increased 300-fold and 10-fold, respectively, in the 90 min following the infusion. The present data suggest that the concentration of sulphydryls in the urinary tract and, more importantly, the intracellular availability of cysteine increase markedly following parenteral glutathione. The high intracellular concentration of cysteine may protect against cisplatinum and oxazaphosphorine toxicity either directly or indirectly by supporting the synthesis of glutathione.
The Lancet, Jul 1, 1980
The accumulation of bile acids has been implicated in the pathogenesis of pruritus of cholestasis... more The accumulation of bile acids has been implicated in the pathogenesis of pruritus of cholestasis. To study the effect of bile-acid depletion on pruritus, 8 patients with chronic cholestasis and intractable pruritus which had not responded to cholestyramine and/or phenobarbitone underwent plasma perfusion through USP-charcoal-coated glass beads. DSuring twenty-two perfusions, between 957 and 6100 ml of plasma were perfused through charcoal columns, resulting in the removal of 126-795 mumol of bile acids. The mean extraction of the perfused bile acids was 81%. After the perfusions, all patients had prompt relief of their pruritus, lasting from 24 h to 5 months. Although the clinical effect may be due to the removal of unidentified pruritogens other than bile acids, charcoal plasma perfusion may improve the quality of life of incapacitated patients with servere intractable pruritus of cholestasis.
Gastroenterology 90(5 Part, Sep 2, 1986
Therapeutische Umschau. Revue thérapeutique, 1987
The Journal of laboratory and clinical medicine, 1979
Removal of protein-bound cholephilic substances such as BA by sorbent perfusion might improve the... more Removal of protein-bound cholephilic substances such as BA by sorbent perfusion might improve the quality of life of patients with severe inoperable cholestasis where the accumulation of BA is thought to be responsible for the often distressing pruritus. Since hemoperfusion is associated with hematological side effects, plasmaperfusion which, in addition, allows the use of novel, possibly more efficient sorbents, might be preferable, provided a substance with a high affinity for these protein-bound anions could be found. A number of sorbents suitable for plasma-perfusion were therefore tested in vitro as to their BA-adsorbing capacity. U.S.P. charcoal coated onto glass beads in order to facilitate perfusion removed BA from human plasma far better than conventional charcoal suitable for hemoperfusion, charged and uncharged resins, and immobilized albumin. The extraction of BA by the coated glass beads exceeded 90% up to a load of 0.18 mumol BA per milliliter of sorbent, and the BA-ad...
The International Journal of Artificial Organs, 1980
Patients with severe, inoperable cholestasis and intractable pruritus not responding to conventio... more Patients with severe, inoperable cholestasis and intractable pruritus not responding to conventional medical therapy might benefit from a depletion of their bile acid pool by sorbent perfusion since accumulated bile acids are possibly responsible for their itching. In vitro, USP-charcoal-coated glass beads removed bile acids from human plasma far better than any other sorbent tested. In order to demonstrate the safety and efficacy of charcoal plasmaperfusion in vivo, five dogs underwent plasmapheresis one week following cholecystectomy and bile duct ligation, and 2.2 ± 0.2 (x̄ ± SD) times their plasma volume was passed over a column containing 400 ml of charcoal-coated glass beads prior to reinfusion. During the procedure the plasma bile acid concentration was reduced by 40.2 ± 4.0% and the bilirubin level by 48.2 ± 3.3%. The columns, whose capacity was far from being saturated, retained 1.3 ± 0.4 times the pre-perfusion plasma pool of bile acids (1.1 ± 0.2 for bilirubin) suggesting...
Journal of Hepatology, 2005
PubMed, Apr 25, 1992
Excessive consumption of ethanol results in reversible redox changes in the liver that are mainly... more Excessive consumption of ethanol results in reversible redox changes in the liver that are mainly responsible for the accumulation of triglycerides and the fatty liver of the alcoholic patient. In spite of continuing alcohol abuse, only a fraction of all alcoholics will develop alcoholic hepatitis and eventually cirrhosis. Genetic predisposition and environmental factors (in particular the often poor nutrition of the alcoholic) probably play an important role in the evolution of these complications. The generation of reactive oxygen species increases during the metabolism of ethanol, but their pathogenetic role in alcoholic liver disease in man is not clear. Acetaldehyde, a metabolite of ethanol, can react with proteins and form stable adducts. Such neoantigens may elicit an immunologic response which could in part be responsible for the liver cell damage associated with excessive alcohol consumption. Since no satisfactory animal model for alcoholic liver disease exists, the relative importance of the various factors involved in alcoholic liver disease is difficult to assess.
PubMed, Feb 1, 1998
Only about 15% of the subjects abusing ethanol will eventually develop cirrhosis of the liver, su... more Only about 15% of the subjects abusing ethanol will eventually develop cirrhosis of the liver, suggesting that other factors in addition to the consumption of large quantities of ethanol play a role in the pathogenesis of alcoholic cirrhosis. Important contributors may be infection with hepatitis viruses, in particular HCV, protein-calorie malnutrition and immunologic factors. Abstinence improves the prognosis of patients with alcoholic cirrhosis, provided that the liver disease is not too far advanced. No pharmacotherapeutic intervention has shown a convincing improvement of the prognosis of alcoholic liver disease, so that the therapeutic efforts should be mainly directed towards abstinence. The patient with alcoholic liver disease needs support and guidance by the treating physicians. Supportive treatment with Disulfiram, Acamprosate or Naltrexon can help with achieving durable abstinence.
PubMed, Sep 21, 1985
Metabolism of drugs by the drug-metabolizing enzyme system usually results in the formation of le... more Metabolism of drugs by the drug-metabolizing enzyme system usually results in the formation of less toxic substances that are readily excreted. A major advance in toxicology, however, has been the observation that the same enzyme system can also activate innocuous drugs into reactive and highly toxic metabolites. Depending on their chemical nature, these metabolites either covalently bind to cellular macromolecules, give rise to toxic oxygen species, or react with membrane lipids to form lipid peroxides. Glutathione, vitamin E and possibly other antioxidants play an important role in protecting the cell from these toxic species. Alteration of a cellular protein by a chemically reactive metabolite may lead to the formation of an antigen and result in an allergic reaction with not only hepatic, but also systemic, manifestations. The formation of toxic metabolites has been postulated in the hepatotoxicity of acetaminophen, isoniazid, halothane, erythromycin and valproic acid. With other drugs, altered pharmacokinetics in the poor metabolizer phenotype and elderly patients may predispose to toxic reactions.
PubMed, Jul 1, 1977
Because of the discovery of uric acid urolithiasis in rats after end-to-side portacaval anastomos... more Because of the discovery of uric acid urolithiasis in rats after end-to-side portacaval anastomosis (PCA), uric acid metabolism was studied in these animals and in appropriate controls. Hyperuricemia and hyperuricosuria were observed in all experimental rats. The fraction of purine catabolites excreted in the urine as uric acid increased from an average of 4.8% to 15.3%. If 14C-uric specifically labeled at position 6 (6-14C-ua) was infused intravenously and the exhalation of 14CO2 was used to calculate a hepatic uric acid clearance, it decreased from 2.14 to 0.97 ml/min/100 gm despite a normal content of hepatic uricase activity as measured in liver homogenates. The fraction of the filtered amount of uric acid excreted in the urine increased from an average of 11% to 30%. Increased supersaturation of the urine with uric acid after PCA may be expected to contribute to the formation of uric acid urolithiasis. This investigation defines a hepatic and renal functional defect in uric acid metabolism which occurs as a result of the PCA.
PubMed, Jul 1, 1984
Ethanol-induced depletion of hepatic glutathione has been construed as evidence supporting the hy... more Ethanol-induced depletion of hepatic glutathione has been construed as evidence supporting the hypothesis that reactive oxygen intermediates generated during the metabolism of ethanol lead to glutathione oxidation and lipid peroxidation and are responsible for the toxic effects of ethanol. However, the evidence for a pathogenetic role of lipid peroxidation in ethanol-induced liver injury is indirect and a decreased synthesis might well account for the glutathione depletion produced by large doses of ethanol. In order to determine whether a decreased synthesis or an increased consumption of glutathione is responsible for the ethanol-induced glutathione depletion, hepatic glutathione turnover, plasma glutathione and the biliary excretion of glutathione and its disulfide were measured in rats. The administration of 5 g/kg of ethanol p.o. resulted in a decreased incorporation of labeled cysteine and labeled methionine into the hepatic glutathione pool and decreased the hepatic concentration of glutathione from 3.7 +/- 0.1 to 2.7 +/- 0.2 mumol/g. Kinetic analysis of the specific activity-time curves revealed that ethanol decreased significantly the rate of influx of cysteine into the glutathione pool but did not stimulate the rate of consumption of glutathione. Moreover, the plasma concentration of glutathione and the biliary excretion of glutathione disulfide and reduced glutathione decreased after the administration of ethanol, indicating that ethanol does not increase the efflux of glutathione from the liver. Our data demonstrate that a large dose of ethanol does not produce an oxidative stress, which would increase glutathione consumption, but rather impairs glutathione synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)
Journal of Applied Physiology, Jul 1, 1988
Endotoxin-induced oxidative stress is investigated in rats by measuring changes in plasma and lun... more Endotoxin-induced oxidative stress is investigated in rats by measuring changes in plasma and lung tissue levels of glutathione disulfide (GSSG) using a modified enzymatic assay that allows simultaneous measurement of up to 80 samples. Salmonella enteritidis endotoxin (2 and 20 mg/kg) acutely increased both plasma reduced glutathione and GSSG with a rise in the ratio of GSSG to total glutathione. This increase in GSSG was enhanced by pretreatment with 1,3-bis(2-chloroethyl)1-nitrosourea (BCNU), an inhibitor of the glutathione reductase enzyme. However, there was no significant arteriovenous difference in plasma GSSG across the lung, and lung tissue GSSG did not increase after endotoxin treatment. The increase in plasma GSSG was not blocked by vinblastine-induced neutropenia and could not be reproduced by incubating rat blood in vitro with endotoxin. Receptor antagonists of platelet-activating factor (PAF), at a dose that previously inhibited endotoxin-induced lung injury, attenuated the endotoxin-induced increase in plasma GSSG. We conclude that endotoxin causes neutrophil-independent oxidative stress in rats, which may be enhanced by the action of platelet-activating factor.
PubMed, Dec 1, 1985
The plasma concentrations of isoniazid and its hydrazino metabolites, acetylisoniazid, acetylhydr... more The plasma concentrations of isoniazid and its hydrazino metabolites, acetylisoniazid, acetylhydrazine and diacetylhydrazine, were measured by gas chromatography-mass spectrometry in 12 healthy subjects after the ingestion of 300 mg of isoniazid. The area under the plasma concentration-time curve of acetylisoniazid and diacetylhydrazine increased with increasing rate of acetylation of isoniazid. In contrast, the area under the plasma concentration-time curve of acetylhydrazine, the postulated precursor of a toxic metabolite formed from isoniazid, was greater in slow acetylators. This occurred even though rapid acetylators generated more acetylisoniazid and thus more acetylhydrazine from isoniazid, because the rapid acetylators also acetylated acetylhydrazine faster to diacetylhydrazine than did the slow acetylators. Due to this complex relationship between area under the plasma concentration-time curve of acetylhydrazine and the rate of isoniazid acetylation (i.e., a faster rate of formation of acetylhydrazine is accompanied by a faster clearance to diacetylhydrazine), the rate of acetylation of isoniazid minimally influences the exposure of most patients to acetylhydrazine. This pharmacokinetic analysis, however, also shows that the apparent plasma half-life of acetylhydrazine is about five times longer than the plasma half-life of isoniazid, and thus repeated doses of isoniazid should lead to an accumulation of acetylhydrazine in the slowest acetylators in which the plasma half-life of acetylhydrazine is 20-plus hr.(ABSTRACT TRUNCATED AT 250 WORDS)
PubMed, Apr 1, 1991
L-2-oxothiazolidine-4-carboxylic acid (OTC), a prodrug of cysteine, was administered at a dose of... more L-2-oxothiazolidine-4-carboxylic acid (OTC), a prodrug of cysteine, was administered at a dose of 0.15 and 0.45 mmol/kg to healthy volunteers. The plasma concentration of OTC reached a peak between 45 and 60 min after p.o. administration. The p.o. clearance of 0.15 mmol/kg of OTC was 0.57 +/- 0.20 liters/(hr.kg) S.D.. The peak increase in plasma OTC was followed by an increase in the plasma concentration of cysteine which rose by 18 to 75 microM over the average basal concentration of 17 microM. The plasma concentrations of free glutathione and total glutathione (i.e., glutathione in small molecular and protein mixed disulfides) did not change significantly during 8 hr after the ingestion of OTC. In contrast, there was a significant increase in the average concentration of cysteine from 0.37 to 0.99 nmol/mg of protein and of glutathione from 8.7 to 15.6 nmol/mg of protein in lymphocytes 2 to 3 hr after ingestion of OTC. The present data shows that OTC is a prodrug of cysteine after p.o. administration in humans and that OTC can raise the circulating concentration of cysteine and the intracellular concentration of cysteine and glutathione in lymphocytes.
PubMed, Oct 1, 1985
Although diquat produces massive oxidant stress in both Fischer and Sprague-Dawley rats, the Fisc... more Although diquat produces massive oxidant stress in both Fischer and Sprague-Dawley rats, the Fischer rats sustain hepatic necrosis and the Sprague-Dawley rats do not. A previous example of probable hepatic necrosis produced by an oxidant stress-generating compound was demonstrated in animals in which glutathione peroxidase activity had been decreased by a dietary deficiency of selenium. In the present study the susceptible Fischer rats had hepatic peroxidase activities equal to the resistant Sprague-Dawley rats. Hepatotoxic doses of diquat did not diminish hepatic glutathione peroxidase or reductase activities or hepatic content of ascorbic acid, NADPH or protein sulfhydryls. Hepatic nonprotein sulfhydryls were decreased by 50% but recovered to control values by 6 h. Biliary excretion of oxidized glutathione in the Fischer rat after administration of diquat was 4 times that observed after administration in Sprague-Dawley rats. The diquat-induced peroxidation of hepatic lipids was indicated by small increases in the 11-, 12-, and 15-hydroxyeicosatetraenoic acids, as quantitated by a new gas chromatography-mass spectrometry assay. Thus, acute lethal injury caused by redox cycling compounds that generate reactive oxygen species does not exhibit a number of the biochemical alterations in vivo that occur with cell death produced by similar compounds in isolated hepatocyte systems.
PubMed, Apr 1, 1980
We have validated a method to assess hepatic glutathione turnover in individual animals in vivo. ... more We have validated a method to assess hepatic glutathione turnover in individual animals in vivo. This method would be applicable to man by collection of bile samples via nasoduodenal intubation. The rate of glutathione turnover was calculated from the time course of the specific activity of the glutathione-acetaminophen adduct in bile after the administration of a radiolabeled glutathione precursor and a small dose of acetaminophen. Identical results were obtained with radiolabeled glutathione or with radiolabeled cysteine, glutamic acid or glycine as the precursors. The small dose of acetaminophen administered to trap glutathione as an excretable adduct did not stimulate glutathione turnover, which reflects glutathione synthesis under steady-state conditions. No evidence for two pools of glutathione with different half-lives was found; previous reports of two glutathione pools may have failed to account for hepatic protein turnover with subsequent release of radiolabeled amino acids for glutathione synthesis. In male rats, the rate of glutathione turnover decreased from 0.52 per hr at 6 weeks of age to 0.12 per hr at 24 weeks of age. After acute depletion of glutathione by diethylmaleate, the rate of glutathione turnover promptly doubled in all age groups. Similar increases in the rate of glutathione synthesis and in the ability to stimulate glutathione production in response to acute depletion in children might explain their decreased susceptibility to acetaminophen hepatotoxicity.
PubMed, Feb 1, 1976
Current in vivo methods do not give information about the drug-metabolizing capacity (Vmax) and t... more Current in vivo methods do not give information about the drug-metabolizing capacity (Vmax) and the affinity of the microsomal enzyme system for the drug i.e., the dose yielding Vmax/2 (Kd). To explore the possibility of estimating these variables from demethylation rates measured by 14CO2 exhalation, various doses of 14C-aminopyrine were injected i.v. to unanesthetized rats. Drug clearances based on 14CO2 exhalation agreed well with those derived from plasma disappearance rates. Evaluation of dose-response curves revealed saturation phenomena. In the normal rat, a Vmax of 173 nmol/min/100 g and Kd of 26 mumol/100 g could be calculated. Enzyme induction with phenobarbital increased Vmax to 745 nmol/min/100 g, whereas in the rat with portacaval shunt, it was reduced to 45 nmol/min/100 g. After 48-hour bile duct ligation, Vmax was not significantly different from the controls, but Kd increased to 36 mumol/100 g compatible with a competitive type of inhibition of aminopyrine demethylation. Two-thirds hepatectomy reduced Vmax by only 50% suggesting that a substantial portion of demethylation occurs extrahepatically. The approach presented appears to be a valid alternative to conventional plasma clearance methods allowing interpretation of some mechanisms affecting in vivo drug metabolism under various conditions.
European Journal of Clinical Investigation, Feb 1, 1991
Parenteral glutathione has therapeutic potential for targeted delivery of cysteine equivalents. T... more Parenteral glutathione has therapeutic potential for targeted delivery of cysteine equivalents. Thus, high doses of reduced glutathione (GSH) protect from the nephrotoxic and urotoxic effects of cisplatinum and oxazaphosphorines. In order to elucidate the underlying mechanisms the kinetics and the effect of glutathione on plasma and urine sulphydryls were studied in 10 healthy volunteers. Following the intravenous infusion of 2 g m-* of glutathione the concentration of total glutathione in plasma increased from 17.5 k 13.4 pmol 1-' (mean+SD) to 823rt326 pmol I-'. The volume of distribution of exogenous glutathione was 176 k 107 ml kg-and the elimination rate constant was 0.063 k0.027 min-' corresponding to a half-life of 14.1 k9.2 min. Cysteine in plasma increased from 8.9 & 3.5 pmol I-' to 114k45 pmol I-' after the infusion. In spite of the increase in cysteine, the plasma concentration of total cyst(e)ine (i.e. cysteine, cystine, and mixed disulphides) decreased, suggesting an increased uptake of cysteine from plasma into cells. Urinary excretion of glutathione and of cyst(e)ine was increased 300-fold and 10-fold, respectively, in the 90 min following the infusion. The present data suggest that the concentration of sulphydryls in the urinary tract and, more importantly, the intracellular availability of cysteine increase markedly following parenteral glutathione. The high intracellular concentration of cysteine may protect against cisplatinum and oxazaphosphorine toxicity either directly or indirectly by supporting the synthesis of glutathione.
The Lancet, Jul 1, 1980
The accumulation of bile acids has been implicated in the pathogenesis of pruritus of cholestasis... more The accumulation of bile acids has been implicated in the pathogenesis of pruritus of cholestasis. To study the effect of bile-acid depletion on pruritus, 8 patients with chronic cholestasis and intractable pruritus which had not responded to cholestyramine and/or phenobarbitone underwent plasma perfusion through USP-charcoal-coated glass beads. DSuring twenty-two perfusions, between 957 and 6100 ml of plasma were perfused through charcoal columns, resulting in the removal of 126-795 mumol of bile acids. The mean extraction of the perfused bile acids was 81%. After the perfusions, all patients had prompt relief of their pruritus, lasting from 24 h to 5 months. Although the clinical effect may be due to the removal of unidentified pruritogens other than bile acids, charcoal plasma perfusion may improve the quality of life of incapacitated patients with servere intractable pruritus of cholestasis.