Rapid assessment of the distribution of apolipoproteins C-II and C-III subspecies in triglyceride-rich lipoproteins by isoelectric focusing.

We describe an isoelectric-focusing method for rapidly separating and quantifying apolipoprotein (apo) C-II and C-III subspecies of triglyceride-rich lipoproteins. Concentrated very-low-density lipoproteins (VLDL) or delipidated apo VLDL are focused on dry acrylamide plates, after their rehydration with ampholytes and urea. Apo C-II and apo C-III in VLDL are resolved into four major bands--C-II (pI 5.01), C-III0 (pI 5.10), C-III1 (pl 4.92), and C-III2 (pI 4.84)--at the same pI values as for purified apo C. This precise technique can be used without delipidating VLDL. The relative percentage of C apoproteins found in VLDL from plasma of normal subjects agreed with previously published data. The ratio of apo C-II to apo C-III decreased in patients with chronic renal failure or with coronary artery disease.