13C NMR investigation of cholesterol esterification rate in human whole blood

We have previously used NMR spectroscopy to measure the acyl transfer from phospholipid to cholesterol in human plasma. In the present study we investigated the processes of transfer of cholesterol and exchange of cholesteryl ester between lipoproteins during incubation of human whole blood. The rate of cholesteryl ester increase was much greater during whole blood incubation (86-118, mean = 90 mumol l-1 h-1) compared to plasma incubation (53-93, mean = 57 mumol l-1 h-1). The rate of decrease in unesterified cholesterol was identical to cholesterol ester increase during plasma incubation, but was slower during whole blood incubation, consistent with replenishment by transfer of additional unesterified cholesterol substrate from erythrocyte membranes. The analysis of lipoprotein fractions revealed an increase in cholesteryl ester content of d < 1.063 lipoproteins; the rate of increase was 47-67 with a mean of 58 mumol l-1 h-1. Although this result is comparable with that obtained by other methods, it represents the product of both CETP and beta-LCAT activity. These NMR techniques provide simple and direct assessment of aspects of reverse cholesterol transport and warrant further investigation.