Enzyme histochemistry of aging rat kidney

Aging-dependent changes of some enzymatic activities related to the glycolytic anaerobic pathway (lactate-dehydrogenase, LDH), to the Krebs's cycle (succinate dehydrogenase, SDH) and to the activity of the respiratory oxidative chain (NADH2 - tetrazolium reductase, NADH-D) were studied in the nephron of 4-(young) and 24- (aged) month-old female Wistar rats. In the renal glomeruli LDH and NADH-D activities were reduced with aging, while SDH did not undergo aging-dependent changes. In both the proximal and the distal convoluted tubules, LDH reactivity slightly increased while NADH-D remarkably decreased in old rats; SDH did not show aging-dependent changes. In the loop of Henle LDH was slightly increased, SDH was unchanged and NADH-D was decreased in aged in comparison to young rats. The three enzyme activities investigated were significantly reduced in the collecting tubules of aged animals. The above results are suggestive of the existence of aging changes in mechanisms related with energy transduction in the rat kidney, affecting at a different extent the cell populations of the nephron.