Apolipoproteins (apo) C-I, C-II, and C-III play crucial roles in intravascular lipid metabolism. Whereas apo C-II is an obligate cofactor for lipoprotein lipase, apo C-III was shown to inhibit its action. Apo C-I can be a potent cofactor of human lecithin:cholesterol acyltransferase. Structural mutants and deficiencies of apo C-II lead to hypertriglyceridemia. A similar phenotype is associated with apo C-III mutants and is inducible by overexpression of human apo C-III in transgenic animals. No structural variant has so far been reported for apo C-I. The present paper describes a rapid semi-automated procedure for isoelectric focusing analysis of these C-apolipoproteins from whole plasma or serum and their visualization by immunofixation and silver staining. The procedure allows detection of charged variants of C-apolipoproteins. As applied to 295 patients with coronary heart disease and 85 controls, it also serves to detect deficiency syndromes of these apolipoproteins. The procedure provides reliable, easy and quick analysis of C-apolipoproteins applicable as a routine or screening procedure not restricted to specialized laboratories.

The underlying cause of the increased electrophoretic mobility of VLDL and HDL in XRI patients remains unclear. Future studies should investigate other apolipoproteins and verify the cholesterin sulfate concentrations reported for VLDL and HDL from XRI patients.