Induction of follicular growth by exogenous interleukin-8

Although the effects of inflammatory cytokines such as interleukin (IL)-1 and tumour necrosis factor (TNF)-alpha on ovulation have been investigated, there are few reports concerning the effect of IL-8 in the ovary. We examined the localization of IL-8 in the human ovary, and also investigated the number of IL-8 staining cells in a section of 1 mm2. The number of IL-8 staining cells was 10 +/- 4.8 in the proliferative phase, 2.0 +/- 1.9 in the secretary phase, and 2.4 +/- 2.2 in the postmenopausal phase respectively. The increased number of IL-8 staining cells could be shown in the human ovarian medulla/stroma during the proliferative phase. By serial section analysis of the ovary, the localization of IL-8 corresponded with mast cells. When immature rats were injected with pregnant mare serum gonadotrophin (PMSG) followed by an i.p. injection of human IL-8, ovarian vasodilatation and follicular growth were observed. Exogenous IL-8 induced a similar increase in follicular growth to that produced by the luteinizing hormone (LH) surge. At 6 h after IL-8 (20 microg) i.p., the follicular size was increased to almost the same size as human chorionic gonadotrophin (HCG) i.p. However, at 24 h after IL-8 i.p., the follicular size decreased. The size of follicular growth was almost the same size as control when <2 microg IL-8 was injected. At 6 h after IL-8 (10 microg) local injection, the follicular size in rats was similar to that observed with IL-8 (20 microg) i.p. We conclude that IL-8 is one of the important cytokines in the ovulatory process.