[Functional and structural vascular reactions following intermittent administration of angiotensin in spontaneously...

In order to find out whether after repeated intermittent treatment with angiotensin-II (A-II) the hypertrophically and hyperplastically altered vascular walls show the same adaptation as with normotensive rats (NR), investigations were performed on 44 male 16-week-old spontaneously hypertensive rats (SHR) (Okamoto-Aoki). In three repeated series daily doses of 0.15 mg depot A-II, the lowest blood pressure effective dose attended by vascular and organic reactions, were applied for 5 days. We found that the functional reactivity of the arterial vascular system in SHR was retained after repeated intermittent administration of A-II despite the hypertrophically hyperplastic processes. This was equally true for the structural reactivity as shown by the occurrence of equal vascular alterations following each new injection series as those which appeared after the first administration of A-II. Thereafter, no structural adaptation of the arterial vascular system occurred in the SHR. The extensive A-II induced vascular alterations did not lead in SHR to additional sustained increase in blood pressure. On discontinuation of A-II treatment the A-II-induced vascular alterations reconverted within a month, even after repeated intermittent A-II treatment, despite the existence of high blood pressure. They are thus reversible. A similar remission is observed also with the A-II-induced myocardial alterations. It thus becomes obvious that, with maintained reactivity of the vascular walls against A-II and with an existing hypertension, R-A-S stimulating factors obviously are able to induce structural alterations at the arterial vessels.