Heterogeneity of purified human pituitary luteinizing hormone: effect on hormone measurement by radioimmunoassay.

Purified preparations of human luteinizing hormone (hLH), Hartree IRC-2, and NIH LER-960, have been examined after gel filtration of unlabelled and iodinated hormone. Several peaks of radioactivity were observed corresponding to dimeric (peak I), monomeric (peak II), and sub-unit (peak III) lLH forms. The immunologic and receptor activities of each fraction have been evaluated, Receptor activity was found in peaks I and II but not in peak III. Within peak II all fractions were not equally active in the receptor assay, and maximum activity appeared to correspond to molecules with elution characteristics similar to the unlabelled molecule. All fractions of peak II were immunologically active when tested against rabbit anti-hCG in excess. Two immunoassay systems with improved specificity for hLH and hLH-alpha, respectively, have been employed to show the presence of alpha subunit in one of the hLH preparations. These data have relevance with respect to testing of immuno and receptor potencies of hLH preparations.