[Age-related changes in adenylate cyclase activity, lipid composition and lipid peroxidation in rat intestinal mucosa: comparison with the frequency of spontaneous tumors].

The study used 3, 7, 16 and 22 month-old male rats bred at the animal farm of the Institute. Identical age-related changes were established in the level of free cholesterol, its esters, free cholesterol/phospholipids and sphingomyelin/lecithin ratios in ascending and descending colon mucosa. Unlike descending colon mucosa, the basal and hormone-stimulating activity of adenylate cyclase and rate of lipid peroxidation in the mucosa of the ascending colon of 22 month-old animals were lower than in 16 month-old rats. The results are compared with the available data on the predominant localization of spontaneous tumors in the proximal (ascending) part of rat's intestine.