Ovarian clock affected by hormonal signals

Ovulation may be partly dependent on an ovarian circadian clock that is affected by hormonal signals from the pituitary, according to animal research published in the September issue of Endocrinology.

Tomoko Yoshikawa, of the Hokkaido University Graduate School of Medicine in Sapporo, Japan, and colleagues analyzed data from female Period1-luciferase (Per1-luc) transgenic rats. Researchers surgically denervated or heterotopically transplanted the ovaries within the animals with or without encapsulating them with dialysis membrane, then phase advanced or delayed the animals' light-dark cycles by 6 hours. They cultured the animals' ovaries during the next 12 days to assess the resetting of their ovarian clock.

Control ovaries had similar resetting trajectories as their surgically denervated or encapsulated counterparts, indicating that endocrine signals can sufficiently provide phase information to the ovary, the authors write. In granulosa cell cultures, follicle-stimulating hormone and luteinizing hormone were associated with large phase shifts of Per1-luc on the following day.

Yoshikawa T, Sellix M, Pezuk P, et al. Timing of the ovarian circadian clock is regulated by gonadotropins. Endocrinology. 2009;150:4338-4347.