A radioimmunoassay for the detection of α1-fetoprotein (AFP) in the sera of rats is described. The procedure is based on the preparation of purified and radiolabeled AFP, monospecific anti-AFP antiserum, and a modification of the coprecipitation-inhibition technique in 50% saturated ammonium sulfate. A detailed description is given of the combination of immunochemical and physiocochemical methods used in the purification of the rat AFP. The purified rat AFP is virtually identical to the native, circulating AFP by immunological criteria and contains, at most, trace contamination with other materials. The radioimmunoassay has a sensitivity that allows 25 ng AFP per ml of serum to be detected with reproducibility. The assay requires 20 µl of serum for analysis and can be completed within a few hours.
Supported by a grant from the Medical Research Council of Canada, Ottawa, Ontario, Canada.