Characterization of the acidic forms of ovine pituitary luteinizing hormone

Abstract

Abstract. The naturally occurring acidic forms of ovine pituitary LH were examined by chromatofocusing. Immunoreactive oLH eluted as six variants (elutions pHs of >7.4, 6.83, 6.59, 6.23, 5.5-4.0, and <4.0, designated as "basic forms" and variants II-VI, respectively). In rams, the percentage in each variant averaged 46, 9, 28, 10, 5 and 2, respectively, of the total LH recovered. oLH from non-implanted wethers or wethers implanted with dihydrotestosterone, E2 or dihydrotestosterone +E2 eluted as six similar variants but differences were noted in the distribution of oLH among the variants. Compared to rams, pituitary extracts from non-implanted and dihydrotestosterone-implanted wethers contained significantly higher percentages of oLH eluting as basic forms. In contrast, E2- or dihydrotestosterone-implanted wethers exhibited significantly higher percentages of oLH in the acidic variants. Each of these variants was demonstrated to contain biologically active oLH using an in vitro bioassay. Furthermore, the basic forms of oLH were the most abundant biologically active forms present in pituitary extracts. These results suggest that in addition to the seven basic forms of oLH previously described, there are at least five naturally occurring acidic forms of oLH in pituitary extracts which are biologically active, and the distribution of pituitary oLH among its isohormones, including the acidic forms, appears to be modified by steroids.