Destruction of the germinal disc region of an immature preovulatory follicle suppresses follicular maturation and ovulation.

Previous work has suggested that the germinal disc and the overlying layer of granulosa cells located near the germinal disc, collectively referred to as the germinal disc region (GDR), is a primary "growth center," regulating granulosa cell proliferation within follicles in the rapid growth phase. This study was designed to determine whether the presence of a viable GDR is required for the completion of follicular maturation and ovulation of the avian follicle. Twelve or 24 h before the expected time of ovulation, the GDR of the largest preovulatory follicle (F1) was destroyed by applying solid CO2 (2 x 2 mm) for 20 sec. A region of the follicle wall equal in size to but opposite the GDR was destroyed in control birds. Blood samples were taken 24 h and 6 h before and at the time of ovulation. The effects of GDR destruction on plasma progesterone (P4), LH, and ovulation were determined. Destruction of the F1 GDR 24 h before ovulation resulted in an absence of the preovulatory rise in plasma P4, attenuation of the LH surge, blocked ovulation, and atresia of the F1 follicle. Controls displayed typical preovulatory profiles of plasma P4 and LH and ovulated at the expected time. In contrast to the data collected after destruction of the GDR 24 h before ovulation, destruction of the GDR 12 h before ovulation did not disrupt ovulation. Furthermore, destruction of the GDR 24 h before ovulation had no effect on basal or LH-stimulated P4 production by granulosa cell cultures prepared 12 h after destruction of the GDR.(ABSTRACT TRUNCATED AT 250 WORDS)