Cholesterol transfer between .ALPHA.- and .BETA.-lipoprotein fractions in serum. Method of estimation and some factors influencing the cholesterol translocation.

An in vitro incubation procedure for the estimation of some cholesterol dynamics in serum was devised, taking advantage of a purified specific goat antiserum against human serum β-lipoprotein to achieve the fractionation of a- and β-lipoprotein fractions. The new method was based on the two principles that the decrease of free cholesterol (FC) in the β-lipoprotein fraction during incubation should represent the amount of FC transferred from β- to α-lipoproteins and that the increase in the amount of esterified cholesterol (EC) in the β-lipoprotein fraction during incubation should be equal to the amount of EC transferred from α- to β-lipoproteins since the esterification of cholesterol occurs only in α-lipoprotein particles. The amount of esterified cholesterol which was transferred from α- to β-lipoproteins was calculated. The values of free cholesterol and esterified cholesterol in α- and β-lipoprotein fractions before and after the incubation were estimated with various serum samples taken from young and old women. The results obtained in this study indicated that the cholesterol dynamics are influenced considerably by several factors, such as LCAT activity, and the levels of cholesterol, triglyceride and phospholipid in the serum. Differences in the cholesterol dynamics between the young and old women indicated the possibility that the new method is useful for investigating the pathogenesis of atherosclerosis.