Effects of antihypertensive agents propranolol, metoprolol, nadolol, prazosin, and chlorthalidone on ACAT activity in rabbit and rat aortas and on LCAT activity in human plasma in vitro.

Various antihypertensive agents were studied in vitro to determine their effects on cholesterol esterification by arterial ACAT (acylCoA:cholesterol acyltransferase; E.C. 2.3.1.26) and on the activity of plasma LCAT (lecithin:cholesterol acyltransferase; E.C. 2.3.1.43). Propranolol inhibited ACAT in normal rat aorta, atheromatous rabbit aorta, and in isolated microsomes from atheromatous rabbit aorta, and in isolated microsomes from atheromatous rabbit aorta. Inhibition reached 50% in microsomes at approximately 0.8 mM. Metoprolol, prazosin, and chlorthalidone also inhibited microsomal ACAT, but to a lesser extent than propranolol; nadolol had no effect on the enzyme. Propranolol, metoprolol, prazosin, and chlorthalidone also inhibited LCAT in human plasma, whereas nadolol showed no inhibitory effect. Fifty percent inhibition occurred at 2 mM with prazosin and chlorthalidone and at 4-5 mM with propranolol. Metoprolol showed a weak dose-dependent inhibition that ranged from 2 to 10% over the concentration range 0.5-5 mM. The data suggest a mechanistic basis for altered lipoprotein profiles observed clinically with certain antihypertensive therapies and suggest that a direct effect of beta-blockers on arterial wall metabolism may account for their recognized ability to reduce the development of experimental atherosclerosis and to improve survival in post-myocardial infarction patients.