Abstract
Observation was made on the localization of adenosinetriphosphatase (ATPase) in the kidney cortex and on its changes following the functioning of the tubule in an attempt to study the activity of ATPase in the proximal tubule. After the rabbits were loaded with glucose, phlorizin and egg-albumin and were subjected to biopsy, they were killed by cervical bleeding and the kidney cortex was removed. The electron microscopic material was treated by the method of Essnner et al. and the microscopic material by a modification of Gomori's method. On the other hand, the cortex homogenate was submitted to cell fractionation according to the method of Schneider-Hogeboom et al. Measurement of ATPase in each fraction was made by means of a partial modification of Iwasa et al. 1. ATPase in the kidney cortex of both the control group and the loaded group showed a strong activity in the cell membrane which was composed chiefly of the brush border of the proximal tubule. Besides the fact that a strong ATPase activity was observed in the blood vessel, the activity was generally weak in other regions. No activity of ATPase in the cell fraction agreed with the findings of histochemical staining; the microsome fraction exhibited the strongest ATPase activity. ATPase activity was present in the sedimentary fraction but was hardly recognized in the supernatant. ATPase can be interpreted as combining with components in the cell. 2. Both histochemical staining and cell fraction determination revealed no apparent change in the activity of ATPase in the rabbits which were loaded with glucose and phlorizin. In the light of this fact, it was presumed that ATPase was not related directly to the reabsorption of glucose. 3. Histological changes in the proximal tubule following the loading of the rabbits with eggalbumin were the hyperf unction of reabsorption or athrocytosis. From the increased activity of ATPase in the region it was inferred that ATPase takes part directly or indirectly in the reabsorption of egg-albumin by the cell membrane. An increase in the activity of ATPase in the mitochondria fraction, a histological increase and change in the number of the fraction led the author to presume that mitochondria indirectly perform some function when egg-albumin is reabsorbed
