The effects of calcitonin on calcium uptake and respiration in rat-liver mitochondria

Abstract

The action of calcitonin on both the transport of calcium across the mitochondrial membrane and cellular respiration has been studied in the presence and absence of added phosphate. In the presence of phosphate, both the rate of calcium entry and the amount of calcium accumulated was stimulated by calcitonin, above a threshold concentration, in a saturable manner. In the absence of phosphate, calcitonin enhanced the rate of calcium entry, but had no appreciable effect on the levels of total calcium accumulated. The minimum concentration of calcitonin necessary to produce these effects was in all cases dependent on the external calcium concentration. Mitochondrial respiration was inhibited only at calcitonin levels much higher than those affecting calcium uptake. These results are consistent with the idea that the action of calcitonin is directly related to the mechanism of calcium uptake, and not to the respiratory process.