The effects of cholesterol feeding on the membranes of liver cells and on the cholesterol metabolism in the rat.

1. Feeding of rats with a 2% cholesterol diet for 6 weeks increased the serum cholesterol concentration. The activity of lecithin cholesterol acyltransferase was also increased during the feeding time. 2. The activities of aspartate aminotransferase and alanine aminotransferase remained on a constant level during the experiment on rats having cholesterol in their diet. Omitting cholesterol from the diet enhanced the activities of both enzymes and the increase in alanine aminotransferase activity was more pronounced. 3. The activity of alkaline phosphatase was on higher level during the whole experiment in the rats having cholesterol in the diet than in those fed a cholesterol-free diet. 4. Present data suggest that excluding cholesterol from the diet labilizes the membranes of hepatocytes and facilitates the release of aspartate and alanine aminotransferases in the blood.