title: Rate of exchange of esterified cholesterol between human plasma low and high density lipoproteins.
abstract: In vitro incubations of human low density lipoproteins (LDL), high density lipoproteins (HDL) and lipoprotein-free plasma at 37 degrees for 6 h revealed no significant net mass transfers of esterified cholesterol from either lipoprotein fraction to the other. Observed transfers of esterified [3H]cholesterol from LDL to HDL must, therefore, have represented a process of molecular exchange between the two fractions. The time course of the esterified [3H]cholesterol transfers indicated that, from the point of view of the exchange process, the pools of esterified cholesterol in LDL and HDL were (mathematically) homogeneous, thus permitting a precise calculation of the rate of the exchange between the two fractions. In incubations of lipoproteins isolated from the plasma of 9 clinically normal human subjects, there was an hourly exchange of 8-12% and 7-31% of the pools of esterified cholesterol in LDL and HDL respectively, which, in molar terms, represented an exchange of 108-301 mumol/l plasma/h between the two fractions. The exchange of esterified cholesterol between human LDL and HDL is, therefore, rapid when considered in relation to other parameters of esterified cholesterol and lipoprotein metabolism.
mesh_terms: D001692:Biological Transport; D002784:Cholesterol / Q000097:blood*; D004951:Esterification; D006801:Humans; D008075:Lipoproteins, HDL / Q000097:blood*; D008077:Lipoproteins, LDL / Q000097:blood*; D013997:Time Factors
chemical_list: D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D002784:Cholesterol