Absence of effect of cardiac denervation and induced right ventricular failure on canine myocardial norepinephrine binding sites.

Abstract

Myocardial sensitivity to catecholamines appears to be altered in chronic cardiac denervation and failure. We have studied in vitro the binding of tritiated norepinephrine (3H-NE) to binding sites in myocardial membrane fractions prepared from canine right and left ventricles. Twenty-six dogs were studied; eight were normal controls, two had sham operations, eight had cardiac denervation, and eight had cardiac failure. Myocardial membranes were incubated with 5 × 10-9 mol/1 3H-NE in vitro and displacement studies with unlabelled norepinephrine performed. Computer-generated Scatchard plots indicated K (affinity constant of binding in 1/mol x 106) and q (number of binding sites in mol/mg of protein x 10-10). No group differed significantly from normal and sham controls. These results suggested that altered myocardial sensitivity to catecholamines in cardiac denervation and failure is not due to altered affinity or concentration of norepinephrine binding sites.