Involvement of leukotriene B₄ in ovulation in the rabbit

The present study was undertaken to assess the effects of lipoxygenase products on ovulation, oocyte maturation, and steroid production in the perfused rabbit ovary preparation. Ovulatory efficiency was significantly reduced when rabbit ovaries were perfused with human CG (hCG) plus nordihydroguaiaretic acid (NDGA) at 10^-5 or 10^-6 M, as compared to contralateral hCG-treated controls. The addition of NDGA to the perfusate inhibited hCG-induced ovulation in a dose-related manner. The percentage of ovulated ova and follicular oocytes achieving germinal vesicle breakdown did not differ significantly between NDGA-treated ovaries and contralateral controls. Leukotriene B₄ (LTB₄) production by the perfused rabbit ovaries reached its maximum 6 h after exposure to hCG and then declined. The addition of NDGA at 10^-5 M significantly inhibited hCG-stimulated LTB₄ production by rabbit ovaries throughout the entire perfusion periods. The ovulatory efficiency in ovaries treated with hCG alone or with hCG plus NDGA correlated significantly with LTB₄ production by perfused rabbit ovaries 6 h after exposure to hCG (α = 0.8893, P < 0.01). Furthermore, the addition of LTB₄ at 100 ng/ml to the perfusate reversed the inhibitory effects of NDGA on hCG-induced ovulation. However, exposure to NDGA affected neither progesterone nor estradiol production elicited by hCG administration. These results suggest that NDGA may block hCG-induced ovulation in vitro, probably via the inhibition of LTB₄ production by rabbit ovaries.