ARGININE-VASOPRESSIN STIMULATES P-32 LABELING OF PHOSPHOINOSITIDES INRAT PINEAL-GLAND

The peptidergic innervation of the pineal gland contains arginine vaso pressin (AVP) fibers. Since the site and molecular mechanism of AVP ac tion on the pineal signal transduction has not yet been determined, we examined whether the inositol phosphate transduction system is involv ed. The phosphoinositide signaling system was studied by measuring met abolic turnover of phosphatidylinositol (PI), phosphatidylinositol pho sphate (PIP) and phosphatidylinositol bisphosphate (PIP2), which refle cts phosphoinositide cycle activation. AVP induced a significant incre ase in P-32 labeling of PI, PIP and PIP2. The V-1 receptor site(s) blo cker for AVP abolished enhanced P-32 labeling of PIP and PIP2. AVP was without effect on cAMP dependent phosphorylation. The data indicate t hat AVP activates the phosphoinositide signaling system via V-1 recept ors and is without effect on the cAMP system.