CARDIOSELECTIVITY OF ATENOLOL

Effects of atenolol on isolated rabbit right atria and guinea-pig tracheal stripe were studied in comparision with propranolol and practolol. The results showed that atenolol, as propranolol and practolol, could cause a parallel shift of the cumulative dose-response curves of isoprenaline to the right. pA2 values of atenolol, practolol and propranolol on rabbit atria were 7.48, 7.22 and 8.67, while those on guineapig tracheal strips were 5.49, 6.33 and 8.76 respectively. Thus, the cardioselectivity index of atenolol was calculated as 1.99, and that of praotolol was 0.89; i. e., the effect of atenolol on β1 adrenoceptors was about 100 times as potent as that on β2 adrenoceptors, and that of practolol on β1 adrenoceptors was only 8 times as that on β2 adrenoceptors. Our results were consistent with the idea that the cardioselectivity of atenolol is higher than that of practolol, and that atenolol could be used clinically in place of practolol.