Angiotensinase A in the renomedullary interstitial cells.

Aminopeptidase A (angiotensinase A; APA) was demonstrated by histochemical means in the renomedullary interstitial cells of the golden hamster, rat, guinea pig and hare. The highest APA activities were shown in the interstitial cells of the hamster. Ultracytochemical studies of the kidney medulla of the hamster indicated that APA is localized mainly on the cell membranes of interstitial cells. Reaction product was also observed intracellularly in the nuclear membrane region. Besides the interstitial cells, APA was demonstrable ultracytochemically in the endothelial cell membranes of medullary blood vessels. Biochemical studies of APA in the renal medulla of experimental animals (sodium loaded and sodium depleted hamsters) have shown that significant changes of APA activities were available only after sodium loading, namely a decrease of APA activities in comparison to control animals. - APA through its degradation of angiotensin, is presumed, to have a bearing on the angiotensin induced prostaglandin biosynthesis of renomedullary interstitial cells.