title: Differential distribution of beta-1 and beta-2 adrenergic receptors in cat and guinea-pig heart.
abstract: The concentrations of beta-1 and beta-2 adrenergic receptors were determined in membranes prepared from the left ventricles and right atria of cat and guinea-pig hearts. The relative densities of the two receptor subtypes were determined by analyzing the kinetics of inhibition of specific [125I]iodohydroxybenzylpindolol binding by drugs previously found to show in vitro selectivity for beta-1 or beta-2 receptors. The right atria (including the sinoatrial node) from hearts of both species contained both beta-1 and beta-2 adrenergic receptors. Although beta-1 receptors predominated, approximately one-quarter of the beta adrenergic receptors in the atria were of the beta-2 subtype. The ventricles contained essentially only beta-1 adrenergic receptors. The densities of beta-1 and beta-2 adrenergic receptors were similar in the atria from both species. The cat left ventricle, however, contained twice as many receptors of the beta-1 type than did the ventricle of the guinea-pig heart. These results may explain previous findings that beta-2 selective drugs have more of an effect on chronotropy than on inotropy.
mesh_terms: D000818:Animals; D002415:Cats / Q000378:metabolism*; D005260:Female; D006168:Guinea Pigs / Q000378:metabolism*; D006321:Heart / Q000187:drug effects; D006325:Heart Atria / Q000378:metabolism; D006352:Heart Ventricles / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000145:classification / Q000187:drug effects / Q000378:metabolism*; D013045:Species Specificity
chemical_list: D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; C011878:iodohydroxybenzylpindolol; D010869:Pindolol