Biol Reprod Keystone Symposia Conference on Frontiers in Reproductive Biology & Regulation of Fertility.
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Biology of Reproduction, Vol 15, 195-205, Copyright © 1976 by Society for the Study of Reproduction

In vitro Binding of Radioiodinated Human Follicle-Stimulating Hormone to Reptilian and Avian Gonads: Radioligand Studies with Mammalian Hormones

PAUL LICHT 1, and A. REES MIDGLEY JR. 1

1 Department of Zoology, University of California, Berkeley, CA 94720 and Reproductive Endocrinology Program, The Department of Pathology, Ann Arbor, Michigan 48104


Human FSH iodinated with the aid of lactoperoxidase (1 2 5I-hFSH) was used to study gonadotropin binding to a variety of reptilian and avian gonadal tissues; gonads were examined from five species of turtle (Chrysemys, Pseudemys, Chelydra, Trionyx and Chelonia), a snake (Thamnophis), a lizard (Anolis) and two birds (chicken and duck). All gonadal tissues, including testes and ovaries and isolated corpora lutea from a turtle, showed high affinity, saturable, specific binding of the 1 2 5I-hFSH. The binding was dependent on tissue concentration, time and temperature; full inhibition curves were obtained with concentrations of unlabeled hFSH ranging from ca. 6-1200 ng/ml (ap 10-10 to 10-7 M). Maximal binding of 1 2 5I-hFSH varied from 5 to 30 percent of the total labeled ligand; it was highest in lizard and snake testes and lowest in bird testes (these values are comparable to those obtained with mammalian gonadal tissues). Nongonadal tissues—thyroid, liver and spleen—from snakes and turtles did not show specific binding.

Radioligand binding analyses with a variety of purified pituitary hormones from four mammalian species revealed that competition for binding of 1 2 5I-hFSH by reptilian gonadal tissues was associated with a high degree of hormonal specificity. High concentrations of growth hormone, prolactin and thyrotropin had no appreciable effect; whereas, FSH of ovine, bovine, rat and human origin all inhibited the binding of 1 2 5I-hFSH at relatively low concentrations. These preparations of FSH ranged in potency from 0.2-3 times that of a highly purified hFSH reference preparation. The binding of 1 2 5I-hFSH to turtle and avian tissues and porcine granulosa cells was also highly specific for FSH; the potency of LH from the four mammalian sources was usually <0.1 percent of the homologous FSH. However, all preparations of LH showed appreciable activity in inhibiting the binding of 1 2 5I-hFSH to snake and lizard tissues. Some preparations of LH, especially bovine, were almost as potent as the homologous FSH in inhibiting 1 2 5I-hFSH binding to snake testes. These results suggest that mammalian FSH and LH may act at the same binding sites in some reptilian tissues, and that the hormonal specificity of reptilian binding sites varies among species.

Note:
ACKNOWLEDGMENTS The authors express their appreciation to Joyce Duncan, Mark Byrne, Hugh Meakin and Dr. Antonella Bona for technical assistance during various phases of this project, and to Martin Feder for aid in statistical programming. Gonadal tissues from the Chelonia were generously supplied by Mariculture, Ltd. with the assistance of Dr. J. Wood. Hormones were gifts of Drs. Harold Papkoff, L. E. Reichert, Jr., John Pierce, A. F. Parlow and the Hormone Distribution Programs of the NIAMMD. This work was supported in part by grant BMS-75-16138 (P.L.) from the National Science Foundation and grant HD-08333 (A.R.M.) from the National Institutes of Health.

Submitted on February 13, 1976
Accepted on April 21, 1976






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Copyright © 1976 by the Society for the Study of Reproduction.