Open AccessCoexistence of β1 and β2-Adrenoceptors in the Rabbit Heart
Author(s) -
OttoErich Brodde,
Franz-Josef Leifert,
Hans-Joachim Krehl
Publication year - 1982
Publication title -
journal of cardiovascular pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.762
H-Index - 100
eISSN - 1533-4023
pISSN - 0160-2446
DOI - 10.1097/00005344-198201000-00007
Subject(s) - practolol , ventricle , dihydroalprenolol , beta (programming language) , population , beta 1 adrenergic receptor , adrenergic receptor , metoprolol , medicine , endocrinology , receptor , alprenolol , propranolol , adrenergic , biology , chemistry , pharmacology , antagonist , partial agonist , computer science , programming language , environmental health
We determined the amount of beta 1- and beta 2-adrenoceptors in right and left atria and ventricles of rabbits. For this purpose inhibition of specific (-)-3H-dihydroalprenolol [(-)-3H-DHA] binding (5 nM) by beta 1-selective (practolol, metoprolol) and beta 2-selective (zinterol, IPS 339) adrenergic drugs was determined and analyzed by pseudo-Scatchard (Hofstee) plots. For both atria, inhibition of binding by the four selective beta-adrenergic drugs resulted in non-linear Hofstee plots, suggesting the coexistence of both beta-adrenoceptor subtypes. From these plots we calculated a beta 1:beta 2-adrenoceptor ratio of 72:28 for the right atrium and of 82:18 for the left. In contrast, only a very small amount of beta 2-adrenoceptors (approximately 5-7% of the total beta-adrenoceptor population) could be detected in the ventricles. For comparison we analyzed the inhibition of specific (-)-3H-DHA binding in tissues with homogeneous population of beta-adrenoceptors (beta 1:guinea pig left ventricle; beta 2: cerebellum of mature rats). For both tissues the four selective beta-adrenergic drugs showed linear Hofstee plots, demonstrating that in tissues with homogeneous beta-receptor population interaction of each drug with the receptor followed simple mass-action kinetics. We conclude that beta 1- and beta 2-adrenoceptors coexist in rabbit atria while the ventricles are predominantly endowed the beta 1-adrenoceptors.