Arginine vasopressin stimulates 32P labeling of phosphoinositides in rat pineal gland

Abstract

The peptidergic innervation of the pineal gland contains arginine vasopressin (AVP) fibers. Since the site and molecular mechanism of AVP action on the pineal signal transduction has not yet been determined, we examined whether the inositol phosphate transduction system is involved. The phosphoinositide signaling system was studied by measuring metabolic turnover of phosphatidylinositol (PI), phosphatidylinositol phosphate (PIP) and phosphatidylinositol biphosphate (PIP 2), which reflects phosphoinositide cycle activation. AVP induced a significant increase in 32P labeling of PI, PIP and PIP 2. The V 1 receptor site(s) blocker for AVP abolished enhanced 32P labeling of PIP and PIP 2. AVP was without effect on cAMP dependent phosphorylation. The data indicate that AVP activates the phosphoinositide signaling system via V 1 receptors and is without effect on the cAMP system.