Increased alpha-adrenergic receptor affinity in resistance vessels from hypertensive rats

alpha-Adrenergic receptor-related properties, specifically, norepinephrine affinity, occupancy and reserve during contraction, were determined in segments of rat resistance arteries. These were obtained from the superior mesenteric bed of spontaneously hypertensive rats and Wistar-Kyoto strain controls. Receptor affinity for norepinephrine in the spontaneously hypertensive rats was significantly greater than that for the Wistar-Kyoto controls. There were no differences in the estimates of receptor occupancy and reserve. This finding taken together with other studies is consistent with the conclusion that increased alpha-adrenergic receptor-mediated sensitivity of vascular smooth muscle of the spontaneously hypertensive rat reflects differences in the agonist site on the alpha-adrenergic receptor.