The immunochemical determination of apolipoprotein A, total apolipoprotein A-I and 'free' apolipoprotein A-I in serum of patients on chronic haemodialysis.

We have determined by radial immunodiffusion the apolipoprotein A content of undelipidated serum samples from 30 patients on chronic haemodialysis and 28 controls using an antiserum against high density lipoprotein (anti-apolipoprotein A). We found that the patients had lower concentrations of apolipoprotein A than the controls. When an antiserum against apolipoprotein A-I was used and the samples were delipidated prior to radial immunodiffusion there was, however, no difference in the total amount of apolipoprotein A-I between the two groups. We were able to explain this difference by measuring the amount of 'free' apolipoprotein A-I after crossed immunoelectrophoresis of undelipidated samples, using the antiserum against apolipoprotein A-I. We found that the patients had a higher level of 'free' apolipoprotein A-I than the control group. Since apolipoprotein A-I inhibits hepatic triglyceride lipase, the increase in triglycerides observed in patients on haemodialysis may be caused by the greater concentration of 'free' apolipoprotein A-I in their serum.