Effects of calcium ionophores on the transport and distribution of calcium in isolated cells and in liver and kidney slices

Summary The effects of calcium ionophores on cellular calcium metabolism were studied in cultured kidney cells, in cells freshly isolated from rat kidney, and in liver and kidney slices. In isolated cells, these ionophores decreased the total cellular Ca content and the mitochondrial Ca.⁴⁵Ca efflux from prelabelled cells was also stimulated even in the absence of extracellular Ca. In slices, the ionophore A23187 increased the total slice Ca and the uptake of⁴⁵Ca. However, the mitochondria isolated from these slices treated with the ionophore had a lower total Ca and a depressed relative radioactivity. These results suggest that the increased cytosolic Ca produced by Ca ionophores may be due to mobilization of intracellular Ca stores rather than to a net shift of Ca from the extracellular fluids to the cell.