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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 acceptors of unesterified cholesterol are small lipid-poor apolipoprotein A-I (apoA-I)–containing high density lipoproteins (HDLs) with pre-&bgr; electrophoretic mobility. These are converted by lecithin:cholesterol acyltransferase into larger spheroidal cholesteryl ester–rich HDLs with &agr; mobility. To study the determinants of the concentration of small pre-&bgr; HDLs in tissue fluids, we collected prenodal peripheral lymph from 34 fasted normal men. By crossed immunoelectrophoresis, the concentration of pre-&bgr; HDLs in lymph averaged 20% of that in plasma. On multiple regression analysis, pre-&bgr; apoA-I concentration in lymph was directly related to pre-&bgr; apoA-I concentration in plasma and independently to &agr; apoA-I concentration in lymph. Similar results were obtained when the same apoA-I–containing particles were quantified by size exclusion chromatography. Lymph pre-&bgr; apoA-I concentration was low in a subject with familial lecithin:cholesterol acyltransferase deficiency, despite a normal plasma pre-&bgr; apoA-I concentration, but was normal in a subject with familial lipoprotein lipase deficiency. These results suggest that the concentration of small pre-&bgr; HDLs in human tissue fluids is determined only in part by the transfer of pre-&bgr; HDLs across capillary endothelium from plasma. Local production, by remodeling of spheroidal &agr; HDLs in tissue fluids, may be equally important. Lipolysis of triglyceride-rich lipoproteins by lipoprotein lipase appears to have little effect.