Substance transport around ovary, thus providing optimal environments for its function. It has long been noticed that just before ovulation, there are dynamic fluid changes within the ovarian bursa, the accumulation and drainage of fluid have been previously implicated to link with the bursa lymphatic system, however, the molecular basis for such rapid fluid transport has not been clarified. In present investigation, we found a transient intra-bursa fluid accumulation and reabsorption within the first 5 hours after PMSG -primed hCG administration. We hypothesized that the rapid fluid regulation within ovarian bursa might be related to the aquaporin family proteins, which are specialized channels for water permeability and showed a wide range of physiological functions. To date, at least nine aquaporin isoforms have been confirmed to be expressed in the male and female reproductive tract. Their specific expression pattern together with their regulation by steroid sex hormones provide indirect evidences of a role for AQPs in reproductive physiology, while the expression of aquaporins in ovarian bursa have not been studied. In this study, we discovered that in adult mouse, pre-ovulation hormonal stimulation induced a rapid fluid accumulation and reabsorption within the ovarian bursa, which is closely associated with the spatial-temporal expressions of two aquaporin proteins AQP2 and AQP5, showing dynamic up and down regulations. At the protein level, AQP2 localized on the peritoneal side while AQP5 on the ovarian epithelial side of ovarian bursa, such interesting Semaphorins are a large family of secreted and membrane bound proteins that act as axonal growth cone guidance molecules arrangements of AQP2 and AQP5 on the distinct compartments suggested their coordinated roles in balancing intra-bursa fluid homeostasis.The ovarian bursa usually contains small amount of fluid except for the substantial increase at the time near ovulation. It has been suggested that the lymphatic stomata within the ovarian bursa might took part in the bursa fluid/substance circulation from the ovarian cavity to the vascular system, mainly due to its closely related structure, and its regulation by steroid hormones. The murine bursa fluid had been described to increase 10 h after hCG administration right before ovulation, and the origin of fluid at this pre-ovulation period was suggested to derive partly from the plasma in the follicle walls and partly from the follicular fluid of ovulating oocytes. Such increased bursa fluid was supposed to lubricate the route by which the ovulated oocytes would pass through later on. In our present study, we found an even earlier and transient intra-bursa fluid accumulation and reabsorption within the first 5 hours after PMSG-primed hCG administration, which seems to be more tightly regulated by hormonal regulation and the coordinated expression of specialized water channel AQP2 and 5. Both AQP2 and AQP5 belong to the classic members of aquaporin family that solely permeable to water. AQP2 is abundantly localized in the principal cells of the kidney, which is critical for the vasopressin-dependent urine concentration.