The Lole of Local Regulator in the Rat Ovary during Ovulatory Process

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A cytokine-induced neutriophil chemoattractant (CINC/gro), which belongs to the interieukin (IL)-8 family, acts as a functional chemoattractant for neutrophils in rats. In the present study, we examined whether CINC/gro contributes to the ovulation process in the rat ovulation system. In rat ovaries, CINC/gro was immunohistochemicaliy recognized in the theca layer of the antral follicle but not in the granulosa cells. To clarify the role of CINC/gro in the ovulation process, CINC/gro protein and mRNA were examined during pregnant mare serum gonadotropin (PMSG)-hCG treatment. CINC/gro protein did not increase as a result of PMSG injection. However, it increased rapidly after hCG injection and peaked at 6 h after hCG.CINC/gro mRNA was also strongly expressed after hCG injection. The increase of CINC/gro protein followed increases in IL 1 p and tumor necrosis factor (TNF). In the whole ovarian dispersate culture, FSH, hCG, IL 1 p, and TNF stimulated the production of CINC/gro protein in a dose-dependent manner. In particular, the stimulatory effects of IL 1β and TNF were stronger than those of gonadotropins. The number of ovulated ooCytes counted under microscopy in the salpinx wash solution was significantly lower in the group which endogenous CINC/gro effect was neutralized by intraperitoneal injection of the antibody to CINC/gro than in the control group. These results suggest that CINC/gro plays an important role in the rat ovulation process by attracting neutrophils. CINC/gro increased just prior to ovulation, and it may be regulated directly by cytokines such as IL 1 Q and TNF and indirectly by gonadotropins