DIETARY ALTERATIONS OF THE MITOCHONDRIAL LIPID PATTERN.

1. Changes in the lipid composition of rat-liver mitochondria from both sexes have been studied in response to normal, fat and fat-cholesterol diets. The cholesterol added to the diet was in low concentrations (0.2%). 2. In the non-phospholipid fraction, normal females had higher mitochondrial cholesterol concentrations than males, and the concentration of the free sterol was decreased in fat-cholesterol-fed females, but not in males. 3. In the phospholipid fraction, normal rats of both sexes had a predominance of mitochondrial lecithin over other phosphatides, but females had slightly higher lecithin concentrations than males. Fat-cholesterol-fed females had equal concentrations of lecithin and kephalin. 4. In the minor phosphatides, normal males had higher concentrations of phosphoinositides than females. The phosphatidic acid plus polyglycerophosphatide concentration was increased above normal in fat-fed females. Fat-cholesterol-fed females had higher concentrations of phosphoinositides than normal. 5. In general, changes in the mitochondrial lipid fractions occurred in female but not in male rats.