Localization of aminopeptidase A (angiotensinase A) in the rat and mouse kidney

Aminopeptidase A (E.C.3.4.11.7; APA) can be demonstrated histochemically in the rat and mouse kidney by light microscopy (simultaneous azo coupling with alpha-Glu-MNA as substrate and high-purity FBB as coupling agent) mainly in the brush borders, glomeruli and portions of the juxtaglomerular apparatus. Sex and species differences are found with regard to enzyme activity and localization. The relation of aminopeptidase A to angiotensinase A was established by inhibition experiments with angiotensin II and III. The following significant differences exist with respect to other aminopeptidases (aminopeptidase M and gamma-glutamyl transferase), which were also demonstrated: APM shows no dependence on calcium ions; APM and gamma-GT are not demonstrable in the glomerulus or juxtaglomerular apparatus.