Functional characterization of basolateral and luminal dopamine receptors in rabbit CCD

Previous studies reported the existence of both D-1- and D-2-like receptors in the cortical collecting duct (CCD). However, especially with regard to natriuresis, it remains controversial. In the present study, rabbit CCD was perfused to characterize the receptor subtypes responsible for the tubular actions. Basolateral dopamine (DA) induced a dose-dependent depolarization of transepithelial voltage. Basolateral domperidone, a D-2-like receptor a ntagonist, abolished depolarization, whereas SKF-81297, a D(1-)like recepto r agonist, showed no significant change. In addition, bromocriptine, a D-2- like receptor agonist, also caused depolarization, whereas SKF-81297, a D-1 -like receptor agonist, did not depolarize significantly. Moreover, RBI-257 , a D-4-specific antagonist, reversed the basolateral DA-induced depolariza tion. In contrast to the basolateral side, luminal DA caused depolarization via a D-1-like receptor; however the change was less than that for basolat eral DA. For further evaluation, Na-22(+) flux (J(Na)) was measured to conf irm the effect of DA on Na+ transport. Basolateral DA also caused a suppres sion of J(Na), and this reaction was abolished by domperidone. These result s suggested that the basolateral D-2-like receptor is mainly responsible fo r the natriuretic action of DA in rabbit CCD.