An immunohistochemical study of bovine antral follicles, with special attention to non-atretic follicles with and without atypical granulosa cells.

Inhibin and oxytocin were immunohistochemically demonstrated in all non-atretic and light-atretic follicles > 2 mm from untreated and pregnant mare's serum gonadotrophin (PMSG)-treated heifers and cows. Immunostaining for luteinizing hormone (LH) and oestradiol was observed in all non-atretic follicles > 4 mm, but only in follicles from PMSG-treated cows. Inhibin and oestradiol immunoreactivity was restricted to the granulosa. Oxytocin and LH immunoreactivity was visualized in both the theca interna and the granulosa. Within the granulosa, LH immunoreactivity was mainly present in cells that were located near the basement membrane. Normal granulosa cells differed from atypical granulosa cells (AGCs) with respect to their ability to bind LH and oestradiol. It is concluded that immunostaining for alpha-inhibin, oxytocin, oestradiol and LH cannot be used as a marker of follicle quality to discriminate between non-atretic follicles with AGCs and non-atretic follicles without AGCs in mid-luteal bovine ovaries.