EFFECT OF INCREASING DOSES OF ANGIOTENSIN-II INFUSED INTO NORMAL AND HYPERTENSIVE WISTAR RATS ON LOW-DENSITY-LIPOPROTEIN AND FIBRINOGEN UPTAKE BY AORTIC WALLS

The effect of 6 days' s.c. infusions of angiotensin II at increasing d oses was determined on the uptake of rat or human low density lipoprot ein (LDL) and of human fibrinogen by aorta in normal and spontaneously hypertensive rats. Rat or human LDL or human fibrinogen was injected i.v. 5 days after the start of infusion, and 24 hr later the radioacti vity of aortic walls was determined. Body weight was almost constant i n control rats and moderately decreased in a dose-dependent way by ang iotensin II. Diastolic blood pressure decreased slightly over 6 days i n control rats and increased transiently at the lowest dose of angiote nsin II and progressively with two higher concentrations. All three an giotensin II concentrations significantly increased the uptake of rat and human LDL and of fibrinogen by aorta. The increase was dose relate d for rat LDL but not for human LDL or fibrinogen. In spontaneously hy pertensive rats of the same age in which blood pressure was higher tha n in angiotensin II-infused rats, protein uptakes were not increased. The blood content of aortic walls was negligible and not altered by an giotensin II. Therefore, the uptake of atherogenic plasma proteins by rat aorta is increased by angiotensin II, but this effect may be indep endent of its pressor action.