Differences between serum and urinary LH in hypergonadotropic states

In an attempt to investigate the relationship between molecular configuration, immunoreactivity, radioligand binding, and biological activity, we compared the elution profiles of immunoreactive and radioligand receptor-active LH following gel filtration over Sephadex G-100 (1.6 X 100 cm column). Samples of sera and urinary acetone-insoluble material from normal cycling women during the LH surge (n = 4) and postmenopausal (n = 2) and castrate women (n = 2) were examined. One major peak of LH immunoreactivity was present in the sera and the urinary samples from all subjects. However, this peak of immunoreactive LH in the urinary precipitate consistently occurred 8-10 fractions later than the peak activity observed in the sera. Despite the differences in the profiles of immunoreactivity between sera and urinary precipitates, the major peak of radioligand receptor activity for LH was observed in the same fractions in all samples and corresponded to the major peak of immunoreactivity observed in the sera. Thus, binding activity was sometimes observed in urinary fractions containing little immunoreactivity for LH. Bioassay of selected fractions using the rat interstitial cell-testosterone assay revealed good agreement between receptor activity and bioactivity but not between immunoreactivity and bioactivity. The ratios of total radioreceptor-active to total immunoreactive LH were consistently higher in the sera than in the urinary precipitates. These data suggest alterations in molecular form during metabolism and/or excretion of LH. Whether these alterations represent differences in peptide structure or merely carbohydrate moieties remains to be determined.