Quantitative determination of apolipoprotein A-I in high-density lipoproteins and 'free' apolipoprotein A-I by two-dimensional agarose gel lipoprotein-'rocket' immunoelectrophoresis of human serum.
A method has been developed for quantitative analysis of 'free' apolipoprotein A-I and apolipoprotein A-I associated with high-density lipoprotein (HDL) in serum. The method utilizes the difference between the rate of electrophoretic migration of apolipoprotein A-I associated with HDL (alpha) and 'free' apolipoprotein A-I (pre-beta) in agarose gel. Apolipoprotein A-I is subsequently quantitated by electrophoresis in a second dimensional gel containing anti-apolipoprotein A-I antibodies. Using this method all apolipoprotein A-I of normal fasting serum was found associated with HDL (n = 16). By contrast, 'free' apolipoprotein A-I accounted for up to 12% of the total in the serum of patients with isolated hypertriglyceridemia (n = 8) or mixed hyperlipoproteinemia (n = 8). Between 30 and 35% of 'free' apolipoprotein A-I was found in one patient afflicted with the apolipoprotein C-II deficiency syndrome. Also, 'free' apolipoprotein A-I could be detected in normal postabsorptive serum. 30 and 90 min following heparin-enhanced lipolysis 'free' apolipoprotein A-I accounted for 23 and 20%, respectively, of the total apolipoprotein A-I of serum. Apolipoprotein A-I associated with HDL remained unaltered. It appears, therefore, that 'free' apolipoprotein A-I is liberated from triglyceride-rich lipoproteins during lipolysis.
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016632:Apolipoprotein A-I; D001054:Apolipoproteins A / Q000302:isolation & purification*; D004587:Electrophoresis, Agar Gel / Q000379:methods; D005215:Fasting; D005260:Female; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D007122:Immunoelectrophoresis / Q000379:methods; D008066:Lipolysis / Q000187:drug effects; D008075:Lipoproteins, HDL / Q000097:blood*; D008297:Male; D008875:Middle Aged
D016632:Apolipoprotein A-I; D001054:Apolipoproteins A; D008075:Lipoproteins, HDL; D006493:Heparin