Wortmannin inhibits the activation of MAP kinase following vasopressin V1 receptor stimulation.

Treatment of rat 3Y1 fibroblasts with vasopressin (AVP) results in a transient activation of MAP kinase as potent as with EGF and serum. An antagonist of vasopressin receptor V1, but not an antagonist of V2, inhibited the AVP-induced activation of MAP kinases, indicating that AVP activates MAP kinases through V1 receptor. Prolonged TPA treatment of cells resulted in partial MAP kinase activation, indicating the presence of PKC-independent pathway. The pathway was inhibited by wortmannin, an inhibitor of PI3-kinase. The results suggest that wortmannin-sensitive molecules such as PI3-kinase, are involved in the V1 receptor-mediated activation of the MAP kinase pathway independent of TPA-sensitive PKC.