Biological and Immunological Properties of Zebra Pituitary Gonadotropins: Comparison with Horse and Donkey Gonadotropins1

Previous studies from this laboratory have described the properties of purified luteinizing hormone (LH) and follicle stimulatinghormone (FSH) from horse and donkey anterior pituitary glands. The present study afforded the opportunity to further characterize these previously purified hormone preparations and to compare them with enriched gonadotropin fractions from zebra pituitary glands. Although a single LH and FSH fraction was usually obtained for each pool of pituitaries, two separate zebra LH and two donkey FSH preparations were generated. Purified hormone preparations from the horse were designated eLH and eFSH. Preparations zLH-A, zLH-B, and zFSH were obtained from zebra pituitaries, and fractions dLH, dFSH-A, and dFSH-B were prepared from donkey pituitary glands. These preparations were analyzed by LH and FSH radioimmunoassays (RIAs), radioreceptor assays (RRAs), LH bioassay, and chromatofocusing. Clear immunological differences were observed between equid gonadotropins. Homologous RIAs for eLH and eFSH did not cross-react similarly, or in a parallel fashion, with gonadotropins from the donkey and zebra. In contrast, RIAs capable of assessing LH or FSH in a wide number of species showed all equid gonadotropin preparations to have considerable activity and to produce parallel dilution curves. Relative to eLH (1.00), zLH-A was found to have higher LH bioactivity: LH RIA (2.50), LH RRA:LH RIA (1.42), and LH bioactivity: LH RRA (2.21) activity ratios. The dLH and zLH-B fractions only differed from eLH in LH RRA:LH RIA activity (0.69 and 0.62, respectively). Only LH from the horse possessed clear intrinsic FSH-receptor-binding activity. While dFSH-A and zFSH were similar to eFSH in FSH RRA:FSH RIA activity, dFSH-B was more potent than eFSH in this respect (2.27 vs. 1.00). Analysis by chromatofocusing revealed similar isohormone elution patterns in all the equid LH preparations. Although isohormones with similar isoelectric values may exist in the equid FSH fractions, the relative amounts of FSH in equivalent isoelectric ranges varied. Donkey FSH contained more acidic material than FSH from the horse and zebra. Zebra FSH possessed more basic material than the other equid FSH preparations. In summary, variations in the immunologial and biological properties of gonadotropins from different equids were detected, depending on the assay systems used for characterization. However, no consistent variations in isohormone chromatofocusing profiles could be correlated with differences in hormonal activities.