Increased suppression of exercise-induced increase in renin by propranolol in Chinese subjects

Abstract

Sensitivity to the hypotensive effect of propranolol differs between Chinese subjects and white subjects. To explore the pharmacodynamic explanation for this difference, eight Chinese subjects (age range, 25 to 42 years) and eight white subjects (age range, 22 to 36 years) were given single doses of 10, 20, 40, and 80 mg propranolol on separate occasions at least 3 days apart. Heart rate, mean blood pressure, norepinephrine, epinephrine, and plasma renin activity were measured at the end of treadmill exercise 2 hours after medication was administered. Propranolol produced a concentration-dependent reduction in mean blood pressure and heart rate in both groups. Concentration-response curves were shifted significantly to the left in Chinese subjects, confirming the increased sensitivity to propranolol of the Chinese. The baseline exercise plasma renin activity was twofold higher (p less than 0.05) in Chinese than in white subjects. The sensitivity to beta-blockade-induced suppression of plasma renin activity was increased in the Chinese, which resulted in a sevenfold higher concentration being required in white subjects than in Chinese to produce the same 50% suppression of exercise plasma renin activity (84.8 +/- 23.2 versus 12.7 +/- 7.4 ng/ml, p less than 0.05). The reduction in exercise heart rate and mean blood pressure produced by propranolol were well correlated to the reduction in exercise plasma renin activity in both populations. There was no significant effect of either race or propranolol on plasma catecholamine concentration after exercise.(ABSTRACT TRUNCATED AT 250 WORDS)