Dopaminergic inhibition of the action of vasopressin on the cortical collecting tubule.

The dopaminergic inhibition of the hydrosmotic effect of vasopressin was studied by in vitro perfusion of the cortical collecting tubule isolated from the rabbit kidney. Arginine vasopressin (AVP) 100 microU/ml increased hydrosmotic water permeability (Pf, 10(-3) cm/s) by 11.4 +/- 1.59. Although dopamine 10(-5) M added alone to the bath did not affect Pf, the combined administration of 10(-5) M dopamine and 100 microU/ml AVP reduced the hydrosmotic effect of AVP to to 2.37 +/- 0.34. This inhibitory effect of dopamine was reversed by the simultaneous addition of 10(-5) M metoclopramide, a D2-antagonist. These observations suggest that dopaminergic receptors also exist in the cortical collecting tubule. The dopaminergic inhibition of the hydrosmotic action of AVP may be at least in part responsible for the diuretic action of dopamine.