Enzyme-linked immunosorbent assay for apolipoprotein C-I.

A non-competitive sandwich enzyme-linked immunosorbent assay for apolipoprotein C-I was developed. Sheep antibody to this apolipoprotein C-I, purified by affinity chromatography, was used for coating the wells of a microtiter plate and as a conjugate with alkaline phosphatase. The linear range of the assay was from 80 ng to 15 ng. It was sensitive down to 5 ng. The intra-assay variation coefficient was 2.8%, and the inter-assay variation coefficient 5.3%. The mean concentration of apolipoprotein C-I was 61 +/- 20 mg/l in healthy normal males, and 65 +/- 19 mg/l in females. Apolipoprotein C-I levels were positively correlated with the total cholesterol concentration in both sexes (p less than 0.002). A significant correlation with triacylglycerol was only observed in males (p less than 0.05). A significant increase of apolipoprotein C-I was observed in type V hyperlipoproteinaemia, and in the only studied case of type III.