ALPHA(1)-ADRENERGIC RECEPTORS IN CARDIAC VENTRICLES OF DAHL RATS

This study was designed to examine the effects of sex, age, and a high -salt diet on cardiac alpha(1)-adrenoceptors in an animal model of gen etic hypertension, the Dahl salt-sensitive rat. Ventricular alpha(1)-a drenoceptors were measured by radioligand binding with [H-3]prazosin i n membrane fractions in Dahl S and R rats of 7, 12, and 15 weeks of ag e. In both S and R rats, the maximal binding (B-max) of alpha(1)-adren oceptor binding was greater in male than in female rats. The B-max dec reased with age in both the S and R strains; at 12 weeks of age, B-max was approximately one-half of that observed at 7 weeks of age in both S and R strains. In the rats fed a high-salt diet, the B-max tended t o be greater in S rats than in R rats at 12 weeks of age and this diff erence became significant at 15 weeks of age. A significant positive c orrelation was found between the B-max and the heart-to-body weight ra tio in the Dahl S and R rats. The dissociation constant (K-d) was not different between male S and R rats at each age. These results suggest that the ventricular alpha(1)-adrenoceptor may be involved in cardiac hypertrophy in Dahl rats.