Biology of Reproduction, Vol 25, 568-572, Copyright © 1981 by Society for the Study of Reproduction

Comparison of the Species Specificity of Gonadotropin Binding to Primate and Nonprimate Corpora Lutea

¹ Department of Physiology, University of Arizona, Health Sciences Center, Tucson, Arizona 85724.

Primate gonadotropins [human luteinizing hormone (hLH) and chorionic gonadotropin (hCG)] were 500-1000 times more effective than nonprimate gonadotropins (ovine, bovine, and porcine LH) in inhibiting ¹²⁵ I-hLH binding to particulate preparations of the corpus luteum from the rhesus monkey. In contrast, all gonadotropins were equipotent in inhibiting ¹²⁵ I-hLH binding to luteinized ovarian tissue from pregnant rats. Moreover, primate gonadotropins were only 10 times more effective than nonprimate gonadotropin’s in competing for LH binding sites in porcine corpora lutea. This comparative study indicates that the apparent species specificity of gonadotropin receptors in the monkey is not due to differences in purity or biological activity (as measured in the rat OAAD bioassay) between hormone preparations. Rather, primate gonadotropin receptors have an increased affinity for primate gonadotropins and a decreased affinity for nonprimate hormones. This study emphasizes that the investigation of gonadotropin action in primate reproduction requires the use of primate gonadotropins.

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ACKNOWLEDGMENTS The authors would like to thank Dr. David E. Blask for his assistance with the rat studies, Barbara Torres for her excellent technical assistance, and Gayle Caulton for her preparation of the manuscript. This work was supported by NIH Grants HD-12333, BRSG (RO-5675), and HL-O7249 and an Upjohn Graduate Fellowship in Physiology.