Renal Phosphatase in Experimental Nephropathies. ∗

Abstract

The specific function of the rich phosphatase content of the kidney is still unknown. Since the kidney is almost invariably involved in metastatic calcification and is often the site of pathologic calcification it seemed possible that by comparing the location of the deposits of lime salts in these conditions with that of the phosphatase something might be learned concerning the relation of this enzyme to renal function.

For this purpose we studied phosphatase, acting optimally at a pH of about 9.0 on sodium glycerophosphate, in the kidneys of normal dogs and of dogs in which a toxic nephrosis has been produced by uranium nitrate, potassium bichromate and bichloride of mercury. We compared sections stained for phosphatase by Gomori's 1 method with the quantity of the enzyme obtained in aqueous extracts of the cortical tissue of the same kidneys as determined by Bodansky's chemical method. We soon found, however, that in kidneys in which pathologic calcification was present, there was no correlation between the quantity of phosphatase revealed by the chemical method and the microscopic picture in the Gomori-stained sections.

We therefore stained 3 consecutive sections of kidneys of the dogs used in these experiments, one with routine hematoxylin and eosin, one with Gomori's 1 stain for phosphatase and one for calcium phosphate only by von Kossa's method. The routine sections revealed the location of necrotic or otherwise damaged tubular epithelium. Sections stained by Gomori's method showed all of the calcium phosphate present in approximately quantitative relations. Normally, phosphatase is present in the marginal zone, next the lumen, of the epithelium lining the proximal convoluted tubules. It is most abundant in the first two-thirds or three-fourths of these tubules, that is, in the labyrinth; less abundant in the straight terminal portion, that is, in the medullary rays and in the outer stripe of the outer zone of the medulla.