Inhibition of Na + /K + -ATPase and of active ion-transport functions in the gills of the shore crab Carcinus maenas induced by cadmium (original) (raw)
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Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 1998
The effect of the heavy metal cadmium on in vitro activities of Na + -K + -ATPase and carbonic anhydrase (CA) in intestine and gills of the European eel, Anguilla anguilla, was analyzed. Na + -K + -ATPase enzymatic activities, measured in intestinal and branchial homogenates, were inhibited by increasing cadmium concentrations (0.5 -50 vM, after 1 h of incubation) in a dose-dependent manner; the maximal inhibition (about 80%) was observed at 5 vM and 50 vM CdCl 2 for the branchial and intestinal Na + -K + -ATPase respectively. Carbonic anhydrase activities, measured in gill homogenate and in cytosolic and brush border membrane fractions isolated from intestinal mucosa, were significantly inhibited by pre-incubation (1 h) with CdCl 2 . Maximal inhibition (about 80%) of branchial CA was noted at approximately 60 vM; higher concentrations evoked no further significant inhibition. Intestinal CA isoforms, cytosolic and membrane-bound, exhibited lower sensitivity to the heavy metal with respect to the branchial CA activity, since the highest concentration of CdCl 2 tested (600 vM) produced an inhibition of about 30% and 50% respectively. The results of the present study suggest that cadmium, by inhibiting the activity of CA and Na + -K + -ATPase enzymes in intestine and gills, could alter both acid-base balance and osmoregulation in teleostean fish.
Inhibition of eel enzymatic activities by cadmium
Aquatic Toxicology, 2000
The aim of the present work was to study the in vitro effect of cadmium on enzymes, such as intestinal and branchial carbonic anhydrase (CA) and Na + -K + -ATPase which play a key role in salt-and osmoregulation and acid-base balance in the teleost fish, Anguilla anguilla. Carbonic anhydrase activities in gill and intestinal homogenates were significantly inhibited by CdCl 2 , the gill CA being more sensitive to the heavy metal (IC 50 for the branchial CA = 9.979 1.03 × 10 − 6 M, IC 50 for the intestinal CA = 3.649 1.03×10 − 5 M, P B0.01). With regards to the intestinal CA activity, it has been shown in a previous study that two isoforms exist, a cytosolic and a brush-border membrane bound. These two isoforms show a different sensitivity to cadmium, with the membrane-bound enzyme less sensitive with respect to the cytosolic one, since it showed still an incomplete inhibition at the highest cadmium concentration tested. The inhibition of all the CA activity tested revealed a time-dependence since it required at least 10 min (1 h for the membrane-bound isoform) preincubation with the heavy metal to appear. Na + -K + -ATPase enzymatic activities, measured in intestinal and branchial homogenates, were inhibited by cadmium in a dose-dependent manner, with the branchial activity being more sensitive to the action of the heavy metal than the intestinal one (IC 50 for the branchial enzyme = 1.3890.09× 10 − 7 M, IC 50 for the intestinal enzyme = 2.86 9 0.02× 10 − 7 M, P B0.01). The most of inhibition of the enzyme appeared without any preincubation with the heavy metal. Mg 2 + -ATPase activity was not significantly altered by the in vitro cadmium exposure either in the gills or in the intestine. These findings observed in vitro could be useful in the understanding of the toxic effects that cadmium elicits on aquatic organisms in vivo. In fact, the impairment of the activity of enzymes which carry out key physiological roles could cause alterations of the physiology of the whole organism.
Marine Biology, 1979
The crab Carcinus maenas (L.) was exposed to radioactively labelled cadmium dissolved in seawater at concentrations of 0.1, I and 10 ppm, the latter concentration being toxic to the crabs (50% mortality after 12.3 days). Net accumulation of cadmium from solution was proportional to the level and time period of cadmium exposure. Total absorbed cadmium levels reached 0.0043 and O.O412 mg Cd g-1 dry weight after 40 days exposure to O.1 and I ppm Cd, respectively, and O.1115 mg Cd g-1 dry weight after 12.3 days average exposure to 10 ppm Cd. The highest tissue concentration was found in the midgut gland, reaching 0.786 mg Cd g-1 dry weight after 12.3 days average exposure to 10 ppm Cd. The midgut gland only contained about 10% of the total cadmium absorbed from solution, while the exoskeleton contained the bulk of absorbed cadmium (59 to 80%) probably passively adsorbed onto the surface. When cadmium was absorbed by the crabs from a food source, the midgut gland contained 16.9% of the total absorbed cadmium whereas the exoskeleton now contained only 22.2%. Ten percent of the cadmium available in the food source (Artemia salina) was accumulated by the crabs. When placed in cadmium-free seawater, crabs that had accumulated cadmium from solution lost 69% of the absorbed cadmium in 10 days, mostly from the exoskeleton which lost 78% of its original absorbed cadmium concentration.
Cadmium, zinc and the uptake of calcium by two crabs, Carcinus maenas and Eriocheir sinensis
Aquatic Toxicology, 2005
The uptake of dissolved cadmium and zinc by crustaceans can usually be explained by the passive process of facilitated diffusion involving a transport protein in the membranes of permeable surfaces. Cadmium ions will also enter via uptake routes for calcium, given the similar size of the two free ions. This study has investigated the interaction of cadmium (and comparatively zinc) and calcium uptake in two crabs that show different permeability responses to changes in salinity, with consequently different effects on the uptake of cadmium and zinc with salinity change. Ca uptake rates in Carcinus maenas decreased in reduced salinity (33-15) with the decreased Ca concentration of the medium and increased if the Ca concentration was increased at salinity 20. It is concluded that Ca uptake over the salinity range 33-15 is via apical Ca channels in gill ionocytes, passively down an electrochemical gradient. The Ca uptake rate of Eriocheir sinensis showed no significant decrease over the salinity range 33-10 (probably because of the small differences in an already low Ca uptake rate in this crab against a background of inter-individual variability), but decreased significantly at salinity 5. Added calcium increased the Ca uptake rate of E. sinensis at salinities 15 and 5, supporting the interpretation that Ca uptake in gills is typically passive via apical Ca channels. Cadmium (but not zinc) inhibited calcium uptake in both crabs at 15 salinity, indicating sharing of Ca channels by Cd, but not at salinity 5 (E. sinensis only) when Ca may be taken up into gill ionocytes by another (active?) physiological process.
Brazilian Journal of Medical and Biological Research, 2001
Whole body oxygen consumption and some hemolymph parameters such as pH, partial pressure of gases, level of ions and lactate were measured in the estuarine crab Chasmagnathus granulata after both acute (96 h) and chronic (2 weeks) exposure to cadmium at concentrations ranging from 0.4 to 6.3 mg/l. In all instances, the crabs developed hemolymph acidosis, but no respiratory (increased P CO 2 ) or lactate increases were evident. Hemolymph levels of sodium and calcium were always increased by cadmium exposure. The chronic toxicity of cadmium was enhanced at 12 salinity, even causing a significantly higher mortality in comparison with the higher salinity (30) used. A general metabolic arrest took place at 12 salinity in the crabs chronically exposed to cadmium, as indicated by decreases of oxygen consumption and P CO 2 , an increase of P O 2 , along with no changes in lactate levels. These imbalances were associated with severe necrosis and telangiectasia in the respiratory gills, probably leading to respiratory impairment and finally histotoxic hypoxia and death of the animals.
2005
The effects of salinity and osmolality differences on the uptake rates of dissolved cadmium were investigated in 3 crabs of different ecologies-the euryhaline common shore crab Carcinus maenas, the extremely euryhaline Chinese mitten crab Eriocheir sinensis, and a more stenohaline crab, the velvet swimming crab Necora puber. This study tests predictions derived from the interpretations of the authors from a study of Zn uptake by the same crabs, in terms of the balance between physicochemical and counteractive physiological effects controlling trace metal uptake rates from solution. As predicted, reduced salinities caused increases in the cadmium uptake rate of E. sinensis as expected from the free metal ion model, with increased free cadmium ion availabilities in conditions of reduced chloride complexation. In the cases of C. maenas and N. puber, however, decreased salinity was associated with reduced cadmium uptake, a result interpreted in terms of a physiological response by these crabs to low salinity offsetting the physicochemical effect of increased free cadmium ion availability. This physiological response may include reductions in apparent water permeability with reduced salinities. Osmolality experiments showed that the physiological responses made by the crabs to decreases in salinity could not be explained simply by responses to changes in osmotic pressure of the medium. The interaction of physiology and physicochemistry controls rates of trace metal uptake from solution by these ecophysiologically distinct crab species.