Vasopressin induced production of inositol trisphosphate and calcium efflux in a smooth muscle cell line.

Phosphatidylinositol metabolism and 45Ca2+ efflux were examined in a vascular smooth muscle cell line (A7r5). [Arg 8]Vasopressin stimulated the rapid formation (measurable at 1 sec) of inositol phosphates in a concentration-dependent manner. The time course for formation of inositol phosphates was similar to that for 45Ca2+ efflux from preloaded cells. The efflux of 45Ca2+ in response to [Arg8]vasopressin could be inhibited by a vasopressin antagonist. This supports the hypothesis that inositol 1,4,5-trisphosphate plays a role in vasopressin stimulated calcium mobilisation from an intracellular source in cultured vascular smooth muscle cells.