The distribution of differently sized HDL particles in the plasma can be assessed by measurement of the fractional rate of cholesterol esterification (FERHDL). We have characterized the isotopic assay and compared it to the enzymatic measurement of the decrease in HDL free cholesterol (mass assay). The normal values of FERHDL were established in 116 apparently healthy individuals. The isotopic assay is particularly sensitive to changes in the incubation temperature above 37 degrees C. The reproducibility of the assay in aliquots of plasma stored at -20 degrees C and -70 degrees C for 3 months and even up to 2 years was high. Intraindividual variability of FERHDL is low. In the subjects in whom FERHDL was measured over a 3-month and 2-5 years' period, FERHDL showed a low variability (97.5 +/- 2.6% and 101 +/- 6.0% respectively in a paired t-test). Comparison of the isotopic assay and the mass assay revealed that the isotopic assay was much more reproducible. Normal values of FERHDL and the HDL subspecies distribution (using gradient gel electrophoresis) were established in 63 men and 56 women. The average values of FERHDL were significantly higher in men (16.8 +/- 4.5%/h) than in women (10.6 +/- 3.6%/h) and correlated well with the distribution of the HDL subspecies. FERHDL radioassay as a highly reproducible method for the assessment of HDL subspecies distribution which may be suitable for both retrospective and prospective studies of diseases of atherogenous origin.

Institute of Physiology Academy of Sciences of the Czech Republic

Cholesterol esterification and atherogenic index of plasma correlate with lipoprotein size and findings on coronary angiography