Regulation of adrenal vascular tone: role of endothelin-1 and nitric oxide.

The adrenal gland is a highly vascular organ, with a highly conserved and well-regulated blood supply. This study was designed to determine the roles of the local vascular regulators, nitric oxide (NO) and endothelin-1 (ET-1), in the regulation of adrenal vascular tone. Using the in situ intact perfused rat adrenal preparation it was found that the ETA receptor antagonist, BQ123, caused a significant increase in perfusion medium flow rate, while the ETB antagonist, RES-701-1, had no effect. Administration of the NO synthesis, inhibitor, L-NAME, or perfusing medium lacking the substrate for NO synthesis, resulted in a significant decrease in perfusion medium flow rate through the adrenal gland. These results suggest that endogenous endothelin causes a tonic vasoconstriction in the rat adrenal gland, mediated by the ETA receptor and that endogenous NO exerts a tonic vasodilatory effect on the rat adrenal.