Mediators of the mitogenic action of human V-1 vascular vasopressin receptors

Arginine vasopressin (AVP) activation of V-1 vascular receptors (V(1)Rs) st imulates cell growth and proliferation in different tissues via cellular si gnaling pathways that remain to be identified. To explore the intracellular mediators of the mitogenic action of V1R, Chinese hamster ovary (CHO) cell s were stably transfected with the human V1R cDNA clone we isolated previou sly. We assessed AVP effects on kinase activation (immunoblotting with phos phospecific antibodies), DNA synthesis (tritiated thymidine uptake), cell c ycle progression (flow cytometry analysis after nuclear labeling with propi dium iodide), and cell proliferation (conversion of the colorimetric reagen t MTS) in the presence or absence of various pathway inhibitors. AVP stimul ation of V(1)Rs leads to the phosphorylation of several kinases, an increas e in DNA synthesis, a progression through the S and G(2)-M phases of the ce ll cycle, and an increase in cell proliferation. The mediators of the mitog enic action of V1R activation included calcium mobilization, coupling to a G(q) protein, and the simultaneous and parallel activation of several kinas es, mainly calcium/calmodulin-dependent kinase II, phosphatidylinositol 3 k inase, protein kinase C, and p42/p44 mitogen-activated protein kinase.