Autoradiographic analysis of changes in ovarian binding of FSH and HCG during induced follicular atresia in the hamster.

Immediately after hypophysectomy, 30 i.u. PMSG were injected s.c. and 3 days later an antiserum to PMSG was injected i.p. Groups of hamsters were killed at 0,24, 48 and 72 h after PMSG antiserum. The ovaries were prepared for topical autoradiography and the numbers of silver grains in different ovarian compartments were counted. The numbers of binding sites for 125I-labelled FSH in the granulosa cells of the antral follicles dropped sharply to 33, 14 and 5% of that at 0 h at 24, 48 and 72 h respectively. Binding of 125I-labelled hCG to granulosa cells declined more slowly, being 47, 27 and 24%, respectively. Binding of 125I-labelled hCG to thecal and interstitial cells was unaffected. Compared to other models of atresia, the changes in gonadotrophin binding observed in this model occur at an accelerated rate because of the acute deprivation of PMSG.