Quantitative measurement of glucose-6-phosphate dehydrogenase in cortical fractions of the rabbit nephron.

A quantitative fluorimetric method is described for estimating the activity of glucose-6-phosphate dehydrogenase in isolated fractions of rabbit nephron from the superficial part of the renal cortex: macula densa, proximal convoluted tubule, distal convoluted tubule and glomerulus. The mean activity in the macula densa region was 2.5 X 10(-18) mol/micrometers 3/min, which was about twice the mean activity of the proximal and distal tubular cells and four times that of the glomeruli. As glucose-6-phosphate dehydrogenase is located in the cytoplasm, the average cytoplasmic enzyme activity of the different tubular cells was calculated: macula densa activity was 4.0 X 10(-18) mol/micrometers 3/min whilst proximal tubular cells showed about a third, and distal tubular cells about a quarter of this activity.