Rate of Disappearance of Cholesterol-C14 from the Bloodstream of Dogs.,

A simplified technic is offered for measuring plasma cholesterol-C14 after intravenous injection of this sterol; it consists of liquid scintillation counting of an alcohol-acetone extract of the plasma. The distribution of cholesterol-4-C14 in 2 normal dogs was calculated from a 60- to 70-day study of plasmatic radioactivity, assuming a 4-compartment mammillary system. Excretory rate constants of 1.5 and 1.6% per day of the retained dose were derived. Preliminary estimates of the “exchangeable cholesterol pool” were made. The size of this pool appeared to increase as serum cholesterol rose, either as the result of a high fat diet or of thyroidectomy.