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Papers by Mohammed BOURAS
Journal of Pharmaceutical Sciences, 1997
The oral uptake of the new fluoroquinolone sparfloxacin was evaluated in the human epithelial cel... more The oral uptake of the new fluoroquinolone sparfloxacin was evaluated in the human epithelial cell line Caco-2 that possesses intestinal enterocyte-like properties when cultured in vitro. The uptake of [14C]-sparfloxacin across the apical membrane of Caco-2 cell monolayers was rapid and similar at 25 and 37 °C. The initial rate of sparfloxacin uptake was not saturable in the 1–200 µM range and was unaffected by metabolic inhibitors (depletion of ATP store or ouabain), indicating that uptake was energy-independent. The absence of competition with other fluoroquinolones or aminocephalosporins showed that the absorption of sparfloxacin did not involved the H+-coupled dipeptide transport system. Our findings suggest that the apical uptake of sparfloxacin by Caco-2 cells mainly involves diffusion, a finding that is in agreement with the high lipophilicity of sparfloxacin. The intracellular-to-extracellular concentration ratio of ∼14 after 60 min of incubation suggests the existence of important binding of sparfloxacin to cell components.
Life Sciences, 1996
Transport of enterostatin (VPDPR) across rat jejunum was investigated usii Grass-Sweetana di&sion... more Transport of enterostatin (VPDPR) across rat jejunum was investigated usii Grass-Sweetana di&sion chambers. The rate of absorption of enterostatii and its metabolites were studied in absence and in presence of diisopropyltluorophosphate (DFP), a serine protease inhibitor. An extensive hydrolysis of enterostatin was observed during incubation with brush border membranes and when exposed to the mucosal side of the jejunal epithelium. No accumulation of enterostatin occured in serosal tissue. Addition of DFP delayed enterostatin disappearance and abolished desarg-enterostatii degradation. Under these conditions, a low amount of enterostatin was able to cross the epithelium intact. Moreover, a substantial amount of des-argenterostatin is absorbed across the jejunal epithelium, probably through passive diffision. Thus, a decreased metabolic activity increased the absorption of a tetrapeptide (VPDP). Dipeptidylaminopeptidase IV, remains a limiting step in transfer of intact enterostatin and its metabolite des-arg-enterostatin across intestinal wall.
Journal of Nutritional Biochemistry, 1999
This study was performed to determine whether intestinal luminal polyamine concentrations are aff... more This study was performed to determine whether intestinal luminal polyamine concentrations are affected by a high soy protein diet when compared with a high casein diet or a normoprotein casein diet. We also determined the effects of these diets, with differences in polyamines content, on mucosal polyamines and ornithine decarboxylase (ODC) activity to assess cell proliferation. Three groups of eight male Wistar rats were fed either a 50% soy protein diet, a 50% casein diet, or an 18% casein diet as a control. After 4 weeks of feeding, both intestinal content and mucosa were recovered. Polyamines were assayed by high performance liquid chromatography. ODC activity was measured by the release of (14)CO(2) from (14)C-L-ornithine. Luminal putrescine and cadaverine concentrations were higher in the jejunum than in the ileum, suggesting an absorptive process. The highest concentrations of intestinal polyamines were observed in rats fed the soy protein diet (P < 0.05). Only minor differences were observed in mucosal polyamines according to the diets. ODC activity was also higher in the intestinal mucosa of rats fed the high soy protein diet (P < 0.05). These results suggest that intestinal luminal polyamine concentrations and ODC activity are modulated by the dietary protein source.
Journal of Pharmaceutical Sciences, 1997
The oral uptake of the new fluoroquinolone sparfloxacin was evaluated in the human epithelial cel... more The oral uptake of the new fluoroquinolone sparfloxacin was evaluated in the human epithelial cell line Caco-2 that possesses intestinal enterocyte-like properties when cultured in vitro. The uptake of [14C]-sparfloxacin across the apical membrane of Caco-2 cell monolayers was rapid and similar at 25 and 37 °C. The initial rate of sparfloxacin uptake was not saturable in the 1–200 µM range and was unaffected by metabolic inhibitors (depletion of ATP store or ouabain), indicating that uptake was energy-independent. The absence of competition with other fluoroquinolones or aminocephalosporins showed that the absorption of sparfloxacin did not involved the H+-coupled dipeptide transport system. Our findings suggest that the apical uptake of sparfloxacin by Caco-2 cells mainly involves diffusion, a finding that is in agreement with the high lipophilicity of sparfloxacin. The intracellular-to-extracellular concentration ratio of ∼14 after 60 min of incubation suggests the existence of important binding of sparfloxacin to cell components.
Life Sciences, 1996
Transport of enterostatin (VPDPR) across rat jejunum was investigated usii Grass-Sweetana di&sion... more Transport of enterostatin (VPDPR) across rat jejunum was investigated usii Grass-Sweetana di&sion chambers. The rate of absorption of enterostatii and its metabolites were studied in absence and in presence of diisopropyltluorophosphate (DFP), a serine protease inhibitor. An extensive hydrolysis of enterostatin was observed during incubation with brush border membranes and when exposed to the mucosal side of the jejunal epithelium. No accumulation of enterostatin occured in serosal tissue. Addition of DFP delayed enterostatin disappearance and abolished desarg-enterostatii degradation. Under these conditions, a low amount of enterostatin was able to cross the epithelium intact. Moreover, a substantial amount of des-argenterostatin is absorbed across the jejunal epithelium, probably through passive diffision. Thus, a decreased metabolic activity increased the absorption of a tetrapeptide (VPDP). Dipeptidylaminopeptidase IV, remains a limiting step in transfer of intact enterostatin and its metabolite des-arg-enterostatin across intestinal wall.
Journal of Nutritional Biochemistry, 1999
This study was performed to determine whether intestinal luminal polyamine concentrations are aff... more This study was performed to determine whether intestinal luminal polyamine concentrations are affected by a high soy protein diet when compared with a high casein diet or a normoprotein casein diet. We also determined the effects of these diets, with differences in polyamines content, on mucosal polyamines and ornithine decarboxylase (ODC) activity to assess cell proliferation. Three groups of eight male Wistar rats were fed either a 50% soy protein diet, a 50% casein diet, or an 18% casein diet as a control. After 4 weeks of feeding, both intestinal content and mucosa were recovered. Polyamines were assayed by high performance liquid chromatography. ODC activity was measured by the release of (14)CO(2) from (14)C-L-ornithine. Luminal putrescine and cadaverine concentrations were higher in the jejunum than in the ileum, suggesting an absorptive process. The highest concentrations of intestinal polyamines were observed in rats fed the soy protein diet (P < 0.05). Only minor differences were observed in mucosal polyamines according to the diets. ODC activity was also higher in the intestinal mucosa of rats fed the high soy protein diet (P < 0.05). These results suggest that intestinal luminal polyamine concentrations and ODC activity are modulated by the dietary protein source.