Effect of labeling of plasma lipoproteins with [H-3]cholesterol on values of esterification rate of cholesterol in apolipoprotein B-depleted plasma

The fractional esterification rate of cholesterol in apolipoprotein B (apoB )-depleted plasma (FERHDL) is a good indicator of particle size distributio n in high density lipoprotein (HDL) and low density lipoprotein (LDL). Howe ver, there has been a discrepancy in the absolute values of FERHDL publishe d by different laboratories. Because the main difference between the method s was in the labeling of lipoproteins with [H-3]cholesterol we investigated the effect of using Coming immunoplates and paper discs as carriers of the labeled unesterified cholesterol. We found that Corning plates trap some H -3-labeled free cholesterol, which is released during incubation at 37 degr ees C. This means that this additional H-3-labeled free cholesterol is expo sed to lecithin: cholesterol acyltransferase (LCAT) for a shorter time and artificially decreases FERHDL Using; paper discs discarded before incubatio n as carriers of the H-3-labeled free cholesterol results in complete label ing of HDL and thus yields higher values of FERHDL.