Immunochemical identification of renin in rat brain and distinction from acid proteases

Abstract

THE direct action of angiotensin II on the central nervous system is well recognised^1–4. There is evidence for the presence in the brain of angiotensinogen⁵, angiotensins^6–9, and angiotensin I converting enzyme^10–12. These findings strongly suggest the presence of a brain renin–angiotensin system which may function independently from the somatic system. Renin-like activity in the brain has also been reported^8,13,14. However, the acid pH optimum of the angiotensin I-generating activity in the brain^13,14 led to the suggestion that this renin-like activity might be due to a nonspecific action of acid proteases released during homogenisation and that intrinsic brain renin might not exist¹⁴. Since this view has a profound implication on the origin and control of brain renin activity, we have sought to obtain an unequivocal answer as to whether the observed renin-like activity is indeed due to renin intrinsic to the brain. Using an affinity column capable of separating renin from general acid proteases, and by making use of specific antibodies to renin elicited by pure pig renin¹⁵. We demonstrate here the presence in rat brain of renin which is clearly distinct from acid protease.