Morphological changes in atretic Graafian follicles during induced atresia in the hamster

Hypophysectomized female hamsters primed with 30 i.u. pregnant mare serum gonadotropin (PMSG) were injected with anti-PMSG serum 72 h later to induce atresia in Graafian follicles. The earliest histological evidence of atresia was seen in the cumulus oophorus at 4 h with a significant increase in pyknotic nuclei. The mural granulosa cells, however, did not show pyknoses until 12 h following anti-PMSG serum. The highest number of pyknotic nuclei in the cumulus oophorus was seen at 24 h, when pseudomaturation of the oocyte occurred. Breakdown of the mural granulosa cells was greatest by 48 h. Morphometric measurements of the follicles showed a significant decline in the thickness and area by the granulosa layer at 48 h following injection of anti-PMSG serum. The thecal compartment showed a decline in number of mitoses at 4 h and 12 h and in area at 48 h. However, no pyknotic thecal cells were observed during the 72 h following injection of anti-PMSG serum. The results support previous work using this model, which showed major biochemical changes in the granulosa cells at 12 and 48 h. The theca, however, was comparatively unaffected during atresia. The various studies using this model show changes in atretic follicles similar to those seen in other models and in the intact animal. The major advantage of this model is that it produces a large synchronous population of follicles that rapidly becomes atretic.