The measurement in vivo of the rate of unesterified cholesterol exchange between rat plasma and erythrocytes.

In order to investigate the rate of unesterified cholesterol exchange between plasma and erythrocytes in vivo, cholesterol labelling in rats was achieved in one of the following ways: intravenous injection of cholesterol-labelled erythrocytes, subcutaneous injection of labelled acetate, feeding of labelled cholesterol. The specific activity of the unesterified cholesterol was measured at intervals up to 24 h and a kinetic analysis of the data was performed. It assumes that both the cholesterol in the erythrocytes and the unesterified cholesterol in the plasma were homogeneous pools. The rate constants obtained for the movements of unesterified cholesterol from erythrocytes to plasma and from plasma to erythrocytes were not significantly different in the three labelling conditions (mean values: 0.26 and 1.5 h-1, respectively).