Concentrations of electrophoretic and size subclasses of apolipoprotein A-I-containing particles in human peripheral lymph

When cultured cells are exposed to plasma, the initial accepters of unester ified cholesterol are small lipid-poor apolipoprotein A-I (apoA-I)-containi ng high density lipoproteins (HDLs) with pre-beta electrophoretic mobility. These are converted by lecithin:cholesterol acyltransferase into larger sp heroidal cholesteryl ester-rich HDLs with alpha mobility. To study the dete rminants of the concentration of small pre-beta HDLs in tissue fluids, we c ollected prenodal peripheral lymph from 34 fasted normal men. By crossed im munoelectrophoresis, the concentration of pre-beta HDLs in lymph averaged 2 0% of that in plasma. On multiple regression analysis, pre-beta apoA-I conc entration in lymph was directly related to pre-beta apoA-I concentration in plasma and independently to alpha apoA-I concentration in lymph. Similar r esults were obtained when the same apoA-I-containing particles were quantif ied by size exclusion chromatography, Lymph pre-beta apoA-I concentration w as low in a subject with familial lecithin:cholesterol acyltransferase defi ciency, despite a normal plasma pre-beta apoA-I concentration, but was norm al in a subject with familial lipoprotein lipase deficiency. These results suggest that the concentration of small pre-beta HDLs in human tissue fluid s is determined only in part by the transfer of pre-beta HDLs across capill ary endothelium from plasma. Local production, by remodeling of spheroidal alpha HDLs in tissue fluids, may be equally important. Lipolysis of triglyc eride-rich lipoproteins by lipoprotein lipase appears to have little effect .