Protein kinase C inhibits arginine vasopressin-stimulated cAMP accumulation via a Gi-dependent mechanism.

Abstract

Studies were performed to identify the site at which activation of protein kinase C (PKC) inhibits arginine vasopressin (AVP)-stimulated adenosine 3',5'-cyclic monophosphate (cAMP) accumulation in cultured rat inner medullary collecting tubule (RIMCT) cells. Neither endogenous stimulation of PKC by epidermal growth factor (EGF) nor the addition of exogenous 1,2-dioctanoyl-sn-glycerol (DOG) impaired forskolin-stimulated cAMP accumulation. Similarly, neither EGF nor DOG altered cAMP generation in response to cholera toxin. However, pretreatment of RIMCT cells with pertussis toxin resulted in loss of inhibition of AVP-stimulated cAMP accumulation by DOG. Likewise, the ability of the phorbol ester, phorbol 12-myristate 13-acetate (PMA), to inhibit AVP-stimulated cAMP accumulation was eliminated by pretreatment with pertussis toxin. PMA also inhibited AVP-stimulated adenylyl cyclase activity in plasma membranes prepared from rat inner medullas. In contrast to its effects on AVP, activation of PKC did not impair cAMP accumulation in response to isoproterenol or prostaglandin E2. These studies demonstrate that PKC-mediated inhibition of AVP-stimulated cAMP accumulation in cultured RIMCT cells requires the intact inhibitory guanine nucleotide binding protein Gi.