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Biology of Reproduction, Vol 25, 752-758, Copyright © 1981 by Society for the Study of Reproduction

Effects of hCG and Cyclic AMP on Aromatization in Purified Leydig Cells of Immature and Mature Rats

LUIS E. VALLADARES 1, and ANITA H. PAYNE 1

1 Reproductive Endocrinology Program, Department of Obstetrics and Gynecology and Department of Biological Chemistry, The University of Michigan, Ann Arbor, Michigan 48109


Aromatization of testosterone to estradiol was assessed in purified Leydig cells of rats 15, 25, and 60-70 days old. Leydig cells obtained after purification by Metrizamide gradient centrifugation were incubated for 4 h with a saturating concentration of [3H]testosterone (0.6 µM). [3H]-Estradiol was isolated and final identity established by recrystallization. Aromatization of [3H]-testosterone to [3H]estradiol was demonstrated in Leydig cells of all ages. Basal aromatase activity per 106 Leydig cells was highest in Leydig cells of 25-day-old rats, intermediate in Leydig cells of 15-day-old-rats, and lowest in Leydig cells of 60-70-day-old rats. At saturating concentrations of [3H]testosterone, human chorionic gonadotropin or dibutyryl cyclic AMP acutely stimulated aromatization in Leydig cells of 25 and 60-70-day-old rats, but not of 15-day-old rats. A potent competitive inhibitor of aromatase, 7agr-(4'-amino)phenylthioandrost-4-ene-3,17-dione, markedly inhibited estradiol production from testosterone in Leydig cells from all ages studied. These results demonstrate that Leydig cells of immature rats have the capacity for aromatization and that this step in steroidogenesis can be acutely stimulated by hCG and cAMP in Leydig cells of 25 and 60-70-day-old rats. The similarity in degree of stimulation of aromatization by dibutyryl cyclic AMP and hCG suggests that acute stimulation of aromatization by hCG is mediated by cyclic AMP.

Note:
ACKNOWLEDGMENTS We thank Dr. Ray Counsell, University of Michigan, Ann Arbor, for providing the 7agr[4-Amino]-phenylthioandrosten-4-ene-3,17-dione. We gratefully acknowledge the technical assistance of Mary Dockrill and E. Elizabeth Floyd.

Submitted on March 9, 1981
Accepted on July 2, 1981




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Copyright © 1981 by the Society for the Study of Reproduction.