Correlation of enzyme histochemical and structural segmentation in the proximal convoluted tubule of the rat kidney. Enzyme activity compared to the freeze-dried structure of serial-sectioned normal rat nephrons.

In the normal rat kidney enzyme histochemical activity was correlated with the structural segmentation of the convoluted part of the proximal tubule, as seen in freeze-dried sections. Serial sections were employed for alternate morphological and enzyme histochemical studies. The tubules were investigated for activity of the following enzymes: 1) non-specific acid phosphatases, 2) non-specific alkaline phosphatases, 3) succinate dehydrogenase and 4) non-specific esterases. Close to the urinary pole acid phosphatase activity was slight in all instances, whilst in the first and second segment a gradual increase in tubular cells with heavy enzyme activity was seen. All tubular cells at the urinary pole showed heavy alkaline phosphatase activity, but there was a gradual increase of cells showing slight enzyme activity in the first and second segments. Succinate dehydrogenase activity was constantly heavy at the urinary pole, and there was a gradual decrease in these cells with heavy enzyme activity along the course of the first and second segments. The pattern of tubular enzyme activity for these three enzymes was independent of the nephron level in the renal cortex. The non-specific esterase activity was, in comparison, uniform throughout the length of the proximal tubule in nephrons from all levels of the renal cortex. This combined enzyme histochemical and morphological investigation demonstrates conclusively that there is a close correlation between structural segmentation and the pattern of enzyme activity of non-specific acid and alkaline phosphatases and succinate dehydrogenase in the proximal convoluted tubule of normal rat kidney.