Controlling factors in the maintenance of plasma cholesterol concentration in the rabbit.

We have investigated factors important in the maintenance of plasma cholesterol concentration in three groups of New Zealand white rabbits fed either a cholesterol-free, commercial stock diet or an atherogenic diet consisting of stock diet supplemented with 0.1% cholesterol and 10% corn oil. When fed stock diet, the plasma cholesterol concentration in female rabbits (164 mg/100 ml) of one strain was significantly greater than plasma cholesterol concentration in males (67 mg/100 ml) of the same strain or in females (62 mg/100 ml) of another strain. Cholesterol absorption and turnover, steroid excretion and tissue cholesterol storage were examined. The percentage of an oral dose of isotopically labeled cholesterol absorbed could not account for group differences in plasma cholesterol concentrations and was not changed by cholesterol supplementation for 3 weeks. Turnover of plasma cholesterol conformed to a two-pool model in rabbits fed stock diet and the atherogenic diet. In rabbits fed the atherogenic diet, the irreversible disposal rate from pool A and total acidic steroid excretion were inversely related to plasma cholesterol concentration. One controlling factor in the maintenance of relatively low plasma cholesterol concentrations in cholesterol-fed rabbits appears to be enhanced bile acid excretion.