Limited hypertensive effect of infusion of angiotensin

Abstract

Though single injections of angiotensin cause extreme rise in arterial pressure, infusion fails to elevate pressure to the degree usually found in experimental renal hypertension. The maximal pressure level obtainable by infusing angiotensin into anesthetized dogs was approximately the same in different dogs and was independent of the initial pressure. The vagus nerves did not importantly influence the "ceiling" response but if arterial pressure was then elevated by carotid occlusion the ceiling was raised. The combination of renal artery constriction and infusion of angiotensin failed to give a higher ceiling than angiotensin alone. In dogs with chronic renal hypertension the ceiling was higher than in normal dogs, presumably because of an upward shift in the range of response of cardiovascular reflexes. The results support the view that compensatory cardiovascular reflexes and tachyphylaxis to large amounts of infused angiotensin suppress the response and that these factors are much less effective in limiting response to quick injection.