ANALYSIS OF BETA RECEPTOR DRUG INTERACTIONS IN ISOLATED RABBIT ATRIUM, AORTA, STOMACH AND TRACHEA

¹ Department of Pharmacology, University of Illinois at the Medical Center, Chicago, Illinois

Several reports of in vivo experiments indicate that some compounds produce "selective" effects on the beta adrenergic receptors of different tissues. One explanation for selectivity is the existence of different types of beta receptors. The present report is an attempt to detect differences in beta adrenergic receptors by determining apparent dissociation constant (K_B) values for certain selective beta receptor blocking agents in rabbit atrium, aorta, stomach and trachea. The K_B for Ay 21,011, a reported selective cardiac beta receptor blocking agent, was about 660 times greater in aorta than atrium and 15 times greater in trachea than atrium. The K_B values of H 35/25, an agent reported to selectively block peripheral beta receptors, were similar in atrium and aorta. Propranolol, a beta receptor blocking agent for which no selective activity has been reported, yielded a K_B 150- fold greater in stomach than the other tissues. Quinterenol, a compound reported to selectively stimulate beta receptors in smooth muscle, was found to be a beta antagonist in atrium but had little or no effect on beta receptors in aorta, stomach or trachea. These results are interpreted to indicate differences in the beta receptors found in the atrium, aorta, stomach and trachea of the rabbit.

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