Human cardiac beta-adrenergic receptors: Subtype heterogeneity delineated by direct radioligand binding

Abstract

Human myocardial beta-adrenergic receptors were directly identified and characterized using the high affinity antagonist radioligand [125I] iodocyanopindolol. Beta1 and beta2 adrenergic receptors were found to coexist in both the left ventricle and right atrium. The relative proportions of the two receptor subtypes were determined by the use of competition radioligand binding and computer modelling techniques employing the subtype selective agents atenolol (beta1 selective) and zinterol (beta2 selective). The left ventricle contains 86 ± 1% beta1 and 14 ± 1% beta2 adrenergic receptors while the right atrium contains 74 ± 6% beta1 and 26 ± 6% beta2 adrenergic receptors. The direct demonstration of beta2 adrenergic receptors in the human heart, with a higher proportion in the right atrium agrees with pharmacologic data and supports the notion that chronotropic effects of adrenergic agonists in man may be mediated by both beta1 and beta2 adrenergic receptors. © 1983.