The C17,20-lyase, 17 alpha-hydroxylase and aromatase activity in rat ovarian granulosa cells stimulated in vivo by gonadotropins

Immature hypophysectomized rats were injected with PMS; some groups received hCG 48h later. The C17,20-lyase activity in the granulosa cells removed from the large preovulatory follicles was estimated by the amount of labelled acetic acid produced from 21 (14C) progesterone or 17-hydroxyprogesterone. 17 alpha-hydroxylase and aromatase activity were measured by the tritium exchange method. Although the granulosa cells contained lyase, it was considerably less than their hydroxylase activity. The remaining tissue, consisting of small follicles and hypertrophied thecal and interstitial tissue, had a great deal more lyase and hydroxylase activity than did the granulosa cells. The results are consistent with the view that granulosa cells can produce estrogen from progesterone and do not require androgen precursors from the theca and/or interstitium.