Histochemistry of angiotensinase A in the glomerulus and the juxtaglomerular apparatus.

The aminopeptidase A (APA; angiotensinase A, E.C. 3.4.11.7) can be demonstrated histochemically (by simultaneous azo coupling) in the glomerulus and JGA of the rat and mouse kidney by light and electron microscopy. In the rat JGA, the APA is localized in Goormaghtigh's cells (mainly at the cell membranes), and in the mouse it is to be found in epitheloid cells (at the cell membranes and in lysosomal structures). From quantitative histochemical investigations of subcortical glomeruli, it can be proven that the aminopeptidase A determined by histochemical means is the angiotensinase A that splits N-terminal aspartate from AI or AII. Animal experiments (sodium depletion, sodium loading, adrenalectomy) bring about marked APA alterations in the glomeruli and in the JGA. The strongest APA alterations can be seen in the adrenalectomized animals, namely an increase of the APA activity in the glomeruli and parts of the JGA. The findings suggest that this enzyme is important for the regulation of the glomerular blood flow and the renin secretion or production by means of angiotensin degradation.