INCREASED BETA-ADRENERGIC-RECEPTOR DENSITY IN AN EXPERIMENTAL-MODEL OF CARDIAC TRANSPLANTATION

  • 1 January 1983
    • journal article
    • research article
    • Vol. 86  (2) , 195-201
Abstract
.beta.-Adrenergic receptor density, basal, maximal isoproterenol and fluoride-stimulated adenylate cyclase activities, and morphologic characteristics of rabbit and rat native and heterotopic isograft cardiac tissue were examined. Four wk after graft placement there were only subtle histologic differences between native and graft tissue. Membrane preparations from isografts of rabbits demonstrated increases in .beta.-receptor density (maximum [3H]DHA [dihydroalprenolol] binding = 111 .+-. 19.3 fmol/mg vs. 52.4 .+-. 4.9 in native hearts, P < 0.05). In a small number of experiments, rat isografts also demonstrated a suggestive increase in .beta.-receptor density (69.8 .+-. 7.1 fmol/mg vs. 40.2 .+-. 7.3 in native hearts). Isoproterenol-stimulated adenylate cyclase activity was greater in rabbit graft hearts (3.98 .+-. 0.20 .times. basal activity) than in native tissue 2.67 .+-. 0.16 .times. basal activity, P < 0.05). Cardiac denervation may lead to a postsynaptic form of .beta.-adrenergic supersensitivity that is due to an increase in .beta.-receptor density.