DIRECT SOLID-PHASE RADIOIMMUNOASSAY FOR CHICKEN LIPOPROTEIN-LIPASE

A direct, noncompetitive immunoassay for chicken lipoprotein lipase [LPL; EC 3.1.1.34] was developed. Antibodies to LPL were purified by immunoadsorption chromatography of goat antisera on an LPL-Sepharose column. Purified anti-LPL immunoglobulins were coupled covalently to hydrophilic polyacrylamide beads by a carbodiimide reagent. An excess amount of these beads was incubated with the sample or the standard to be assayed. The amount of LPL immobilized by the beads was then detected by an excess amount of 125I-labeled anti-LPL immunoglobulin. A linear relationship was obtained between the radioactivity bound and the amount of the highly purified LPL used as a standard. The range of the assay was 0.1-1.1 ng LPL. The assay was specific for chicken LPL and showed no cross-reactivity with liver lipase. It does not distinguish heat-inactivated from catalytically active enzyme species. This assay should be useful in studies of lipoprotein lipase where catalytic activity and enzyme mass need to be quantitated.