Effect of metoprolol on diet-induced atherosclerosis in rabbits.

The effect of metoprolol, a beta 1-blocker, on atherogenesis was evaluated in rabbits fed a diet supplemented with 0.25% cholesterol and 3% coconut oil for 21 weeks. After 7 weeks on the diet, the rabbits were randomly divided into treated (n = 22) and untreated (n = 22) groups. Treated animals received metoprolol subcutaneously by an osmotic pump for 14 weeks, resulting in a plasma level of 774 +/- 69 nM during the investigation. Plasma concentrations of cholesterol, triglycerides, and phospholipids did not differ between the two groups. Nor were there any significant differences between the two groups in plasma concentrations of apolipoprotein A-I, apolipoprotein B, apolipoprotein C-III, and apolipoprotein E measured by electroimmunoassay. At the end of the study, the aortas were cut into three portions and the extent of atherosclerosis was determined by morphometry. The group that had received metoprolol had significantly (p less than 0.015) less atherosclerosis in the aorta (ascending plus arch 37.8 +/- 6.8%, thoracic 32.9 +/- 6.1%, abdominal 19.8 +/- 6.1% of total intimal area; mean +/- SEM) than the controls (ascending plus arch 54.9 +/- 7.1%, thoracic 48.0 +/- 6.2%, abdominal 25.9 +/- 5.5%).