Proliferation of granulosa and thecal cells in germinal disc and non-disc regions during follicular growth in Japanese quail (Coturnix coturnix japonica): Bromodeoxyuridine incorporation in situ

Proliferation of granulosa and thecal cells was analysed during ovarian follicular growth in laying Japanese quail. The birds were injected intraperitoneally with bromodeoxyuridine (BrdU) 10 or 4 h before ovulation, that is, before or after a preovulatory LH surge, respectively, and incorporation of BrdU by follicular tissues was detected immunocytochemically. Cells labelled with BrdU were seldom seen in the most immature follicles in the ovarian cortex, whereas many granulosa and thecal cells were labelled with BrdU in medium-sized white yolky follicles (approximately 13.3% and 14.4% in granulosa and theca layers, respectively). Ten and four hours before ovulation, the granulosa cells in the germinal disc and non-disc regions of the third largest yellow yolky follicle (F3) were labelled with BrdU (approximately 8.4% and 9.4% in germinal disc; 6.1% and 9.0% in the non-disc region), but only those in the germinal disc region were labelled (approximately 5.4% and 4.0%) in the largest yellow yolky follicle (F1). The percentage of thecal cells labelled with BrdU 4 h before ovulation was significantly higher than the percentage labelled 10 h before ovulation, and was higher in F3 (approximately 11.7%) than in F1 follicles (approximately 5.4%) 4 h before ovulation. These results show that proliferation of granulosa and thecal cells occurs in both germinal disc and non-disc regions in growing follicles, but when a follicle matures proliferation is reduced and in the case of granulosa cells it is restricted to the germinal disc region.