Kidney in the aging cat: neutral lipid and adenyl cyclase histochemistry.

Neutral lipid and adenyl cyclase were evaluated to determine their concentrations in the kidney of the aging cat. Kidneys from 24 domestic cats 2 months to 7.5 years old in 6 age groups were examined by light microscopic and histochemical methods. Activity in anatomic components of the kidney was assessed on a quantitative basis for evaluation of mean activity between the age groups. Renal components generally were stable in activity in the cats with advancing age. A significant increase in lipid concentration occurred in the convoluted segments of the proximal tubules with advancing age. In contrast, the straight segments of the proximal tubules displayed a significant decrease in lipid concentration with aging. Significant increases in adenyl cyclase activity were evident with aging in the ascending thick limb of Henle's loop and distal tubules.