2-DIMENSIONAL ELECTROPHORESIS OF PLASMA-LIPOPROTEINS - RECOGNITION OF NEW APO-A-I-CONTAINING SUBPOPULATIONS

Two-dimensional electrophoresis has been used to resolve 12 distinct apo A-I-containing high-density lipoprotein (HDL) subpopulations in human plasma. The subpopulations were quantitated by I-125-labeled, monospecific antibody and phosphor-imaging. Modification and standardization of the agarose electrophoresis (first dimension) enabled us to,recognize new HDL subpopulations. Lipoprotein mobilities in agarose were expressed relative to the mobility of the sample's endogenous albumin. We demonstrated the presence of lipoproteins with mobilities faster than and similar to albumin, as well as subpopulations with mobilities slower than albumin. We refer to these as prealpha, alpha and prebeta, respectively. Lipoprotein molecular sizes were determined with a non-denaturing polyacrylamide gradient gel electrophoresis (PAGE) (2% to 36%) in the second dimension. Internal standard of I-125-labeled proteins of known molecular size was run simultaneously in each gel permitting accurate size determination. We have demonstrated that ultracentrifugally-isolated lipoproteins are different from the native apo A-I-containing subpopulations. The major difference observed was the loss of prebeta1 and prebeta2 particles from the d < 1.21 g/ml fractions to the d > 1.21 g/ml fractions. Possible physiologic and pathologic implications of these findings are also discussed.