The effects of K+-depolarization medium, chelating agents and thiol groups on cadmium uptake and efflux in the guinea-pig taenia coli.
Cadmium uptake by taenia coli was dose-dependent, achieving equilibrium after approximately 60 min of incubation. The SH-blocker, N-ethylmaleimide inhibited cadmium uptake. When muscles were washed with normal medium or that containing 0.5 mM EDTA following 0.5 mM Cd2+ treatment for 60 min, the tissue cadmium concentration reached equilibrium levels after 60 min and approximately 43 or 27% of the initial tissue cadmium concentration was retained, respectively. Both glutathione and dithiothreitol also increased cadmium efflux. However the contractions of glycerinated taenia coli caused by Ca2+ and Mg-ATP, completely returned to control values after washing with 0.5 mM EDTA medium following 0.5 mM Cd2+ treatment for 60 min, suggesting that EDTA seems to exert intracellular effects in glycerinated taenia coli. These results suggest that SH-dependent mechanisms in cadmium uptake play a role in intact taenia coli. In addition, in intact taenia coli, Cd2+ are accumulated in intracellular compartments which EDTA cannot reach and may exert an inhibitory action on internal sites in the cells.
Nasu
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Koshiba
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D000818:Animals; D002104:Cadmium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology*; D003106:Colon / Q000378:metabolism*; D003285:Contractile Proteins / Q000378:metabolism; D004492:Edetic Acid / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000378:metabolism; D009467:Neuromuscular Depolarizing Agents; D011188:Potassium / Q000494:pharmacology*; D013438:Sulfhydryl Compounds / Q000494:pharmacology*; D013997:Time Factors
D002614:Chelating Agents; D003285:Contractile Proteins; D009467:Neuromuscular Depolarizing Agents; D013438:Sulfhydryl Compounds; D002104:Cadmium; D004492:Edetic Acid; D005033:Ethylmaleimide; D011188:Potassium