Abstract
Intravenously and orally administered doses of isotopic cholesterol were utilized to compare cholesterol turnover and absorption in squirrel, cebus, and rhesus monkeys fed cholesterol-free diets containing saturated (coconut oil) or unsaturated (safflower or corn oil) fat. The cholesterol turnover data for the comparison period fit a two-pool model, and the calculated turnover rates, PR
Δ, were best compared between species on the basis of metabolic body size, kg
0.75. Cebus and squirrel monkeys had rates of whole-body cholesterol turnover which were similar and twice that calculated for the rhesus monkey. The percentage of endogenous cholesterol reabsorbed tended to be less in squirrel monkeys than in cebus or rhesus monkeys, but no effect of dietary fat on absorption could be demonstrated with the procedure used, nor did dietary fat affect the overall excretion rate. The most remarkable difference was the decreased fractional removal of circulating cholesterol (metabolic clearance factor) associated with saturated fat feeding, reflecting an elevated plasma cholesterol level without a measurable difference in PR
Δ. Neither the mass of total exchangeable cholesterol in pools A and B nor the flux between pools was changed with saturated fat feeding. A serious constraint of the method was the relative imprecision of the measure. Thus, the redistribution of the mass of circulating cholesterol (20–50 mg/kg) from the plasma compartment into other compartments within pool A or B of monkeys fed unsaturated fat could not be traced with certainty. Nonetheless, the data best support the suggestion that dietary polyunsaturated fat causes redistribution of cholesterol into tissue pools without altering total body balance.