Evaluation of the specificity of a luteinizing hormone beta and alpha subunit assay.

A non-specific antihuman FSH antiserum which is able to bind 125I-labelled FSH, LH, LHbeta and LHalpha subunits, has been shown to contain at least three different antibody populations directed against different parts of the LH and FSH molecule. This antiserum has been used to develop a rather specific radio-immunoassay for determination of the common alpha subunit. Further, by gel filtration it is shown that the LH IRC2/69 preparation contains about 30% of intact LH and about 10% of alpha and LHbeta subunit, respectively. In contrast, the LH 68/40 preparation contains about 96% of intact LH and only small amounts of alpha and LHbeta subunit. Also, a considerable difference in the content of the alpha sub-unit was found between two different FSH preparations. The contamination of the preparations of the intact hormones is shown to have a marked influence on the cross-reactivity of the substances in an LHbeta and alpha subunit radioimmuno-assay.