RENAL-ARTERY SMOOTH-MUSCLE IS REFRACTORY TO CONTRACTION BY ANGIOTENSIN-II

The vasomotor responses of vascular smooth muscle from different vascu lar smooth muscle beds have not been well characterized, The purpose o f this study was to compare the contractile responses of vascular smoo th muscle from two vascular beds, the peripheral vascular bed (carotid artery) and the visceral vascular bed (renal artery) to vasoactive ag onists. Fresh bovine carotid and renal artery smooth muscle contractil e responses to serotonin, endothelin, angiotensin, and dopamine were d etermined in a muscle bath. Serotonin and dopamine cause rapidly devel oping sustained contractions in carotid and renal artery smooth muscle . The magnitude of the contractile response to serotonin is significan tly greater in carotid artery and the magnitude of the response to dop amine is similar between carotid and renal artery. Endothelin induces a slowly developing sustained contraction of greater magnitude in rena l artery. Angiotensin II causes transient contractile responses in car otid artery but renal artery smooth muscle is uniquely refractory to a ngiotensin stimulation, This lack of response to angiotensin II may be protective in the role of the kidney in regulating blood pressure thr ough the renin-angiotensin system. Differences in receptor expression or affinity or in postreceptor cellular signaling events may account f or these differential responses to endogenous vasoactive agonists. (C) 1996 Academic Press, Inc.