Cholesterol metabolism in groups of rhesus monkeys with high or low response of serum cholesterol to an atherogenic diet.

Cholesterol metabolism has been studied in two groups of five rhesus monkeys each that were selected from the upper and lower sextile in the distribution of serum cholesterol concentration while being fed an atherogenic diet. This diet consisted of a basal commercial monkey food supplemented with saturated fat and cholesterol. To determine differences that might be related to the difference in serum cholesterol concentration, parameters of whole body cholesterol metabolism were measured while the animals were fed the supplemented diet again while they were fed the basal diet. Serum cholesterol and triglyceride concentrations were greater in the high-respoonding (HI) than in the low-responding (LO) groups during both diet periods. Percent of luminal cholesterol absorbed was also greater in the HI than in the LO group during both diet periods. The increase in fecal excretion of endogenous neutral steroids during the period when the atherogenic diet was fed was similar in the two groups; however the increase in excretion of bile acids was greater in the HI than in the LO group. The three-pool model was used for analysis of decay of serum cholesterol specific activity after a tracer pulse dose. The mean size of the total miscible body pool and of pools 1 and 3 (but not pool 2) was greater in both groups when the atherogenic diet was fed than during basal diet feeding. The distribution of the increment in total body pool between pool 1 and the peripheral pools was similar in the two groups. The distribution of the increment in cholesterol of pool 1 between serum and other tissues was also similar for the two groups. There was an indication that a constant cholesterol pool size was not attained even after feeding the atherogenic diet for 8 months. This study indicates that the difference in serum cholesterol concentration between LO and HI responders is, in part, a result of differences in rate of intestinal absorption of cholesterol.