抄録
Epidemiological and experimental investigations show that hypertension superimposed by hyperlipidemia accelerates atherosclerosis. However, the mechanism is not clearly understood. We have already reported in the previous paper that prolonged hypertension specifically decreased arterial cholesterol esterase (CE-ase) in SHR and SHRSP resulting in an accumulation of cholesterol and cholesteryl ester in the aorta. To extend these studies, the present investigation was undertaken to examine responses of the arterial enzyme to spontaneous hypertension superimposed by hypercholesterolemia. Effects of hyperlipidemia was examined by giving for 16 weeks either a synthetic diet containg 1% cholesterol and 0.5% cholic acid or the diet depleted of cholesterol to 10 week old normotensive female WKR. Effects of hyperlipidemia superimposed by hypertension was examined with female SHRSP treated likewise. Effects of hypertension superimposed by hyperlipidemia was examined with male and female SHRSP which were given for 16 weeks the cholesterol diet either with or with hypotensive drugs. Rat arterial CEase did not change by hyperlipidemia per se, but was elevated by hypertension superimposed by hypercholesterolemia. Accompanying the change in the enzyme activity aortic cholesterol content increased significantly. On the other hand, there were no differences in aortic CEase activity between hypotensively treated and nontreated SHRSP both hypercholesterolemia. This seems to be due to counteraction between the decreasing effect of hypertension and the increasing effect of hypercholesterolemia on arterial CEase. LPL and NAGA activities were elevated by hypercholesterolemia and hypertension, respectively. These results indicated that acceleration of atherosclerosis due to hypertension superimposed by hypercholesterolemia results from relative deficiency of CEase to increased infusion of serum lipids.
