Pharmacological characterization of rat renal medulla dopamine-sensitive cyclic adenosine monophosphate generating system

Abstract

The dopamine (DA) DA-1 and DA-2 receptors coupled to 3'-5'-cyclic adenosine monophosphate (cAMP) generating system were characterized in membrane particles of the rat kidney medulla. In confirmation of reports using central and other peripheral tissues, activation of DA-1 receptors with DA, apomorphine or SKF 82526 induced accumulation of cAMP. This effect was blocked by the DA-1 receptors antagonist SCH 23390 and by the other DA-2 receptor antagonists fluphenazine and haloperidol. DA-2 receptor responses coupled negatively to the cAMP generating system were obtained by incubating renal medulla membrane particles with DA or SKF 82526 together with SCH 23390. DA-2 receptor responses were also elicited with the receptor agonists quinpirole and bromocriptine in the absence of SCH 23390. These inhibitory effects on cAMP generation were abolished by the DA-2 receptor antagonist l-sulpiride. Our findings suggest that rat renal medulla contains DA DA-1 and DA-2 receptors similar to those found in brain and in other peripheral tissues. The physiological significance of these receptors, if any, should be established in future studies.