Effects of cadmium ions, D-600 and KCN on calcium-45 uptake in smooth muscle of guinea-pig taenia coli.
1. The effects of Cd2+ on Ca2+ uptake was compared with that of D-600 and KCN in guinea-pig taenia coli. Cd2+ inhibited both the phasic and tonic K+ responses, however, D-600 and KCN preferentially inhibited the tonic response. 2. Cd2+ (2 x 10(-6) M) which had no effect on the tissue ATP concentration, inhibited La3+ resistant residual Ca2+ binding at the high and low affinity site. Cd2+ (10(-5) M) which decreased the tissues ATP concentration, markedly inhibited Ca2+ binding at the low affinity site. 3. Both D-600 and KCN showed a greater inhibitory effect on Ca2+ binding at the low affinity site than at the high affinity site. 4. These findings suggest that Cd2+ at low concentration may inhibit Ca2+ influx through Ca2+ channel at surface membrane while at high concentrations (greater than 10(-5) M), Cd2+ would inhibit the accumulation of Ca2+ into low affinity sites relating to energy metabolism at mitochondria.
Nasu
T
T
Department of Veterinary Pharmacology, Faculty of Agriculture, Yamaguchi University, Japan.
Ishida
Y
Y
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002104:Cadmium / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D003106:Colon / Q000187:drug effects; D003486:Cyanides / Q000494:pharmacology*; D005711:Gallopamil / Q000494:pharmacology*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007811:Lanthanum / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D011190:Potassium Cyanide / Q000494:pharmacology*
D002132:Calcium Radioisotopes; D003486:Cyanides; D002104:Cadmium; D005711:Gallopamil; D007811:Lanthanum; D000255:Adenosine Triphosphate; D011190:Potassium Cyanide; D002118:Calcium