Involvement of the luteinizing hormone surge in the regulation of ovary and oviduct clock gene expression in mice

<jats:title>Abstract</jats:title><jats:p>Circadian dysfunction perturbs the female reproductive cycle. In particular, mice lacking the clock gene <jats:italic>Bmal1</jats:italic> show severe infertility, implying that <jats:styled-content style="fixed-case">BMAL</jats:styled-content>1 plays roles in ovulation and luteinization. Here, we examined temporal changes in clock gene expression in the ovary and oviduct before and during gonadotropin‐induced follicular growth, ovulation, and luteinization in sexually immature mice. While the oviduct did not show a drastic change in clock gene expression, <jats:italic>Bmal1</jats:italic> expression in the ovary was higher than that in control mice during the period from 4 to 16 hr after human chorionic gonadotropin (<jats:styled-content style="fixed-case">hCG</jats:styled-content>) administration. <jats:italic>Bmal1</jats:italic> expression reached a maximum at 16 hr after <jats:styled-content style="fixed-case">hCG</jats:styled-content> administration, when follicle luteinization occurred. In an interesting manner, administration of <jats:styled-content style="fixed-case">hCG</jats:styled-content> to ex vivo‐cultured oviduct triggered a shorter circadian period and inevitably resulted in phase advance. Together, our present data suggest that <jats:styled-content style="fixed-case">LH</jats:styled-content> surge induces continuous expression of <jats:styled-content style="fixed-case">BMAL</jats:styled-content>1 in the mouse ovary and modulates circadian phase in the mouse oviduct.</jats:p>