Effects of diltiazem on suppression and regression of experimental atherosclerosis

The effects of diltiazem (a calcium antagonist) on the suppression and regression of atherosclerosis were studied. Thirty-one rabbits were fed a 1% cholesterol (atherogenic) diet together with saline (n = 22) or diltiazem (n = 9) injections. After 10 weeks, seven rabbits that received saline and nine rabbits that received diltiazem were killed. The remaining 15 saline-treated rabbits were then put on a standard (regression) diet for the next 15 weeks with saline (n = 7) or diltiazem (n = 8) injections. Sixteen rabbits given a standard diet were used as controls. At 5 and 10 weeks, the plasma LDL cholesterol level in rabbits on the atherogenic diet with diltiazem was significantly lower than in those on the atherogenic diet with saline. The aortic total cholesterol, esterified cholesterol and calcium contents were also significantly lower in rabbits on the atherogenic diet with diltiazem. After 25 weeks (15 weeks on the regression diet), the differences in aortic total cholesterol and calcium contents between the two groups on the regression diet were not significant; however, the aortic esterified cholesterol content was significantly lower in the regression diet with diltiazem. The results suggest that diltiazem has a favourable effect both on regression and on suppression of atherosclerosis.