Differences in beta-adrenoceptor binding in anterior and inferior myocardial wall microsomes of normal canine left ventricle.
Myocardial beta-adrenoceptor binding was investigated, with (-)3H dihydroalprenolol as radioligand, in microsomes derived from anterior (ALV) and inferior (ILV) myocardial wall sections of the canine left ventricle. Characterisation of specific binding sites revealed a hierarchy of myocardial beta-adrenoceptor binding with greater binding occurring to the anterior than the inferior wall of the left ventricle, under identical experimental conditions. Equilibrium analysis by Scatchard plots suggested a significant (P less than 0.01) difference in the number of receptors (Bmax ALV = 70 fmol . mg-1 protein vs Bmax ILV = 37 fmol . mg-1 protein) with no alteration in the binding affinity of the receptors (KDALV = 10.1 nmol . litre-1 vs KDILV = 6.7 nmol . litre-1). Such differences in the extent of binding of beta-adrenoreceptors in cardiac muscle may be of physiological and pathological significance and may account for the heterogeneity of regional autonomic responses in the heart.
D000319:Adrenergic beta-Antagonists / Q000378:metabolism; D000526:Alprenolol / Q000031:analogs & derivatives*; D000818:Animals; D001665:Binding Sites; D004082:Dihydroalprenolol / Q000378:metabolism*; D004285:Dogs; D006352:Heart Ventricles / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008861:Microsomes / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D013237:Stereoisomerism
D000319:Adrenergic beta-Antagonists; D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D004082:Dihydroalprenolol; D000526:Alprenolol