A histochemical study of alkaline phosphatase of the kidney in bovine fetuses and calves.

This study was carried out to observe the change in the activity of alkaline phosphatase and comparisons were made concerning function and the site of production in the kidney between bovine fetuses and calves. Two fetuses, 7 and 10 months of gestation and five calves, 0.5, 4, 8; 24 hr and 5 months after birth were used. Tissues of the kidney were stained with H.E. and alkaline phosphatase stain. In the fetuses, weak adtivity of alkaline phosphatase was observed inside the uriniferous tubules. In the calf just after birth, all renal tubules were extended and activity of alkaline phosphatase was mainly observed in the brush border of the epithelial cells of the proximal convoluted tubule. In the calf 24 hr after birth, activity of alkaline phosphatase increased conspicuously in the brush border and cytoplasm of the columnar epithelial cells of the promixal convoluted tubule, but was not observed in the glomerulus and distal convoluted tubule. From this study and on the basis of the molecular weight and no observation in Bowman's capsule of alkaline phosphatase of the kidney as noted by other workers, it is suggested that kidney alkaline phosphatase in the brush border and cytoplasm of the proximal convoluted tubules of calves is related to the absorptive function of the kidney and that it is produced in the proximal tubules.