ON THE LOCALIZATION OF SOME PHOSPHATASES IN THREE DIFFERENT SEGMENTS OF THE PROXIMAL TUBULES IN THE RAT KIDNEY

The distribution of several phosphatases in three segments of the proximal tubules was studied in frozen sections of glutaraldehyde-fixed rat kidneys. Two segments of the convoluted tubules were identified by in vivo injection of trypan blue. By increasing the concentration of adenosine triphosphate to 3 mM in the Wachstein and Meisel ATPase medium, a clear segmental differentiation in the reaction pattern of the brush border, cytoplasmic bodies and basal infoldings of the proximal tubules was obtained. The specificity of the reaction was investigated by substituting adenosine diphosphate, adenosine monophosphate or β-glycerophosphate for adenosine triphosphate in the incubation medium and by employing cyanide or fluoride as inhibitors. The reaction pattern was also compared with the localization of acid and alkaline phosphatase activities. In addition, the distribution of glucose 6-phosphatase activity was studied which showed differences in the three segments of the proximal tubules.