Comparison of the redox bioassay with other assays for luteinizing hormone

The cytochemical (redox) bioassay for LH has been compared with established LH assays. Measurements made by redox bioassays were considerably lower than those made by radioimmunoassay in human female plasma samples obtained at mid-cycle. There was no apparent relationship between measurements on incubation media from cultures of sheep pituitary glands made by redox bioassay and the ovarian ascorbic acid depletion (OAAD) assay. After polyacrylamide gel electrophoresis of a crude extract of a human pituitary gland, redox LH measurements were lower than those of the OAAD assay and radioimmunoassay in the cathodal segments of the gel. By contrast, there was reasonable agreement between LH measurements made by radioimmunoassay and redox assay in cathodal fractions from gel electrophroesis of a purified pituitary LH preparation. Follicle-stimulating hormone, and the alpha- and beta-subunits of LH depressed the response of intact LH in the redox assay; this might explain the relatively low levels of LH measured by redox assay in some of the experiments described. Which type of assay best reflects the biological activity of LH in man remains to be determined.