Biochemical observations on rat aorta: interaction of dietary protein and cholesterol.

1. The effect of cholesterol feeding during and after a period of protein malnutrition lasting 4 weeks was examined in the rat. Indices measured were plasma total cholesterol, triglycerides and protein levels, and aorta total cholesterol, triglycerides, hexosamine and hydroxyproline concentrations. 2. In both plasma and aorta, total cholesterol and triglycerides levels were higher in the low-protein diet group than in the standard-protein diet group, when cholesterol was supplied in both diets. 3. During the malnutrition period, cholesterol feeding led to a greater decrease in plasma protein than that promoted by the low-protein diet without cholesterol, while aorta hexosamine levels decreased to a lesser extent. 4. Cholesterol feeding with a standard-protein diet promoted a slight and temporary increase in aorta hydroxyproline levels, while a decrease in aorta hexosamine concentration was observed. Cholesterol feeding with the low-protein diet, on the other hand, also promoted a decrease in aorta hexosamine levels but to a lesser extent. 5. During the recovery period, cholesterol feeding impaired the return of plasma protein, aorta hexosamine and lipid levels to that of the control values. 6. These findings demonstrate that cholesterol feeding promotes different changes in aorta and plasma, depending on whether or not protein is supplied by the diet in adequate amounts. This point could be important in relation to the development of atherosclerosis during recovery from a period of malnutrition.