The effect of diets containing different proportions of butterfat and maize oil on plasma lipids and aortic atherosis in rabbits

Abstract

1. Seven groups of male rabbits (thirteen to fifteen per group) were givenad lib. a diet consisting of 80 parts of a low-fat basal ration to which were added 20 parts of fat in the form of butterfat, maize oil or various mixtures of the two.2. After 40 weeks, samples of blood were taken and the animals were killed. The concentrations of total cholesterol and phospholipid in the plasma and the fatty acid compositions of the plasma cholesteryl esters and phospholipids were determined. The degree of atheromatous degeneration was determined in the aortas.3. Little aortic atherosis was observed in the rabbits given the diets containing 0, 10 and 12% butterfat, but as the butterfat content of the diet was increased above 12%, pronounced increases occurred in the extent of atheromatous degeneration of the aorta. The concentration of cholesterol in the plasma increased progressively as the butterfat content of the diet was increased and the maize oil content was decreased. There was an inverse curvilinear relationship between the degree of aortic atherosis and the phospholipid: cholesterol ratio in the plasma.4. The concentration of linoleic acid in the plasma cholesteryl esters was inversely related to the concentration of cholesterol in the plasma, and the concentration of linoleic acid in the plasma phospholipids was inversely related to the concentration of phospholipids in the plasma. There was a positive linear relationship between the stearic: palmitic acid ratio and the linoleic: oleic acid ratio in the plasma phospholipids.