The effects of progesterone and RU486, a synthetic anti-progesterone, on ovarian 3β-hydroxysteroid dehydrogenase (3β-HSD) activity, a key enzyme of progesterone production, were studied during ovulation in immature 22-day-old rats primed with pregnant mares' serum gonadotrophin (PMSG) and human chorionic gonadotrophin (hCG). Ovarian 3β-HSD activities had increased significantly 4 h after hCG injection. These increases were inhibited at 4 and 6 h after hCG when 20 mg RU486 kg−1 was administered 2 h before hCG. However, RU486 had no influence on the activity of 3β-HSD when administered at the same time as hCG injection. A histochemical study revealed that 3β-HSD activities in the granulosa cell layer, but not in the theca cell layer, were inhibited when RU486 was given 2 h before hCG. Serum progesterone concentrations, but not oestradiol concentrations, were significantly suppressed by RU486 treatment 4 and 6 h after hCG. The effect of progesterone on ovarian 3β-HSD activity was tested by administering graded doses of progesterone exogenously to rats 2 h before hCG injection. Ovarian 3β-HSD activity was increased in a dose-dependent manner, and more than 20 mg progesterone kg−1 significantly stimulated the activity. Although 10 mg progesterone kg−1 did not stimulate ovarian 3β-HSD activities, the RU486-inhibited activities were recovered by the concomitant administration of 10 mg progesterone kg−1 with RU486. These results indicate that ovarian 3β-HSD activity depends on progesterone concentrations, and suggest an autocrine regulation of progesterone production during ovulation in immature rat ovaries stimulated with PMSG and hCG.
N. Tanaka, J. Iwamasa, K. Matsuura and H. Okamura
K. Nishimura, N. Tanaka, A. Ohshige, Y. Fukumatsu, K. Matsuura and H. Okamura
The effect of macrophage colony-stimulating factor (M-CSF) on folliculogenesis and ovulation was studied. Folliculogenesis and ovulation were induced in immature female rats with a s.c. injection of equine chorionic gonadotrophin (eCG), followed 48 h later by human chorionic gonadotrophin (hCG). The ovulation rate was measured after the following treatments. (1) Graded doses of human M-CSF (1–300 × 103 iu per rat) were administered i.p. daily for 3 consecutive days. (2) M-CSF (100 × 103 iu) was administered i.p. at designated times between 96 h before and 10 h after hCG injection. (3) Rabbit anti-human M-CSF polyclonal antibody (5 μg) was administered into the left ovarian bursa at designated times between 49 h before and 10 h after hCG injection. In addition, the effect of M-CSF on ovarian macrophages was investigated using immunohistochemistry with mouse anti-rat macrophage monoclonal antibody, TRPM-3. The treatment with M-CSF (> 30 × 103 iu per rat) significantly increased the ovulation compared with controls in a dose-dependent manner. This stimulatory effect of M-CSF was observed when it was administered between 96 h and 49 h before hCG injection. The ovarian intrabursal administration of anti-M-CSF antibody significantly inhibited the number of ovulated ova from the treated ovaries compared with either those from control rats or from the contralateral untreated ovaries between 24 h before and 3 h after hCG injection. The immunohistochemistry revealed that M-CSF increased the number of ovarian macrophages in growing follicles. The results suggest that M-CSF is involved in the process of folliculogenesis and that it promotes ovulation by influencing ovarian macrophages.