Effects of cadmium ions, D-600 and KCN on calcium-45 uptake in smooth muscle of guinea-pig taenia coli

Abstract

1. 1. The effects of Cd 2+ on Ca 2+ uptake was compared with that of D-600 and KCN in guinea-pig taenia coli. Cd 2+ inhibited both the phasic and tonic K + responses, however, D-600 and KCN preferentially inhibited the tonic response. 2. 2. Cd 2+ (2 × 10 −6M) which had no effect on the tissue ATP concentration, inhibited La 3+ resistant residual Ca 2+ binding at the high and low affinity site. Cd 2+ (10 −5M) which decreased the tissues ATP concentration, markedly inhibited Ca 2+ binding at the low affinity site. 3. 3. Both D-600 and KCN showed a greater inhibitory effect on Ca 2+ binding at the low affinity site than at the high affinity site. 4. 4. These findings suggest that Cd 2+ at low concentration may inhibit Ca 2+ influx through Ca 2+ channel at surface membrane while at high concentrations (> 10 −5M), Cd 2+ would inhibit the accumulation of Ca 2+ into low affinity sites relating to energy metabolism at mitochondria.