Vasopressin stimulates the incorporation of [32P]Pi into phosphatidylinositol but not into other phospholipids in rat thoracic aorta strips. The relative abilities of three vasopressin analogues to stimulate phosphatidylinositol labelling in rat aorta are similar to their relative pressor potencies in vivo and to their relative potencies in stimulating the metabolism of rat hepatocytes, but very different from their relative antidiuretic potencies. The vasopressor antagonist [1-(beta-mercapto-beta, beta-cyclopentamethylenepropionic acid),8-arginine]vasopressin competitively inhibits [Arg8]vasopressin-stimulated phosphatidylinositol labelling in rat aorta with a pA2 of 8.1. It is concluded that the Ca2+-mobilizing vasopressin receptors (V1-receptors) of the rat aorta stimulate phosphatidylinositol metabolism, probably by enhancing phosphatidylinositol breakdown.
