Mechanisms of rapid desensitization to arginine vasopressin in vascular smooth muscle cells

This study characterized the rapid desensitization induced by arginine vasopressin (AVP) in vascular smooth muscle cells (VSMC) in culture. The Ca2+ mobilization response and, in some experiments, the intracellular pH changes were used as a probe for the desensitization phenomenon. In VSMC, AVP desensitization was homologous, concentration dependent, and occurred in less than 30 s. The desensitization was complete with 10(-7) M AVP. Receptor occupancy was a critical factor in the maintenance of desensitization, since complete hormone washing by acid glycine buffer produced an earlier (less than 5 min) recovery of the cell response, whereas partial hormone washing with saline (pH 7.4) required 15 min to produce any significant recovery. Protein kinase C activation was a significant mechanism in AVP desensitization, because protein kinase C downregulation inhibited the desensitization phenomenon. Receptor internalization was, however, not important for the desensitization phenomenon, since it still occurred at 4 degrees C. Treatment with pertussis toxin did not affect the Ca2+ mobilization response but decreased the AVP-mediated intracellular alkalinization, therefore suggesting that a Gi or Go protein may be involved in some but not all the aspects of the AVP signal transduction and the desensitization phenomena.