Cholesteryl esters in pig liver during atherogenic diets and foreign serum protein infusions

Eight-month-old pigs were fed a diet supplemented with 15% lard (group II) or 15% lard plus 1.5% cholesterol (group III) for 4 months. Five of the animals fed the high fat and cholesterol diet received two i.v. infusions of foreign serum protein (group IV). One group of animals was treated with the same infusions without dietary fat or cholesterol supplement (group V). Liver lipids and serum cholesterol levels were determined. In group II the concentration and fatty acid composition of hepatic cholesteryl esters showed no marked differences from controls (group I). The same findings were present in 2 of 5 animals of group III; in the other 3 animals higher hepatic cholesteryl ester concentrations and predominantly an elevation of monoenoic acid fraction, in one case also a rise of trienoic acid fraction were obtained. These alterations were found in the liver of all animals of group IV. The reverse was observed in the animals which were given the same serum infusions but only the stock diet (group V): a reduction of hepatic cholesteryl ester concentration and no striking alteration in fatty acid pattern. In cryostat sections of all liver specimens no stainable lipid could be detected. There was no correlation between liver and serum fatty acid composition of cholesteryl esters. The total cholesterol levels in serum showed no increase in group V, a slight increase in group II, a moderate increase in group IV, and a marked, partly large increase in group III. These results are discussed in relation to the effect of cholesterol and fat feeding on cholesterol metabolism and essential fatty acid requirement.