Spatio-temporal changes of prolyl 4-hydroxylase in granulosa cells during ovulation in eCG-hCG-treated immature rat ovaries.

The immunolocalization of prolyl 4-hydroxylase (PHase), a key enzyme of collagen synthesis, and the effects of anti-progesterone RU486 on PHase during the ovulatory process in eCG-hCG-treated immature rat ovaries were studied to investigate the mechanisms of tissue repair in follicle walls after follicular rupture. Immunolocalization of PHase was studied using an anti-rat PHase subunit monoclonal antibody, and the amount of immunoreactive PHase was measured by enzymeimmunoassay. No obvious immunolocalization of PHase was observed in theca cells throughout the ovulatory process except just after follicular rupture. In contrast, in granulosa cells, PHase was first observed at 9 h after the hCG injection, and the staining intensity apparently increased from 9 to 15 h, especially around the apex of preovulatory follicles and the orifice of ruptured follicles. Consistent with these observations, PHase concentration in granulosa cells isolated from the ovaries significantly increased by 9 h (0.45 +/- 0.03 pg per cell), and reached a peak at 15 h (0.66 +/- 0.06 pg per cell) after the hCG injection. This peak was inhibited when 20 mg RU486 kg-1 was administered at 8 h (0.46 +/- 0.05 pg per cell), and the RU486-inhibited PHase concentration was recovered by the concomitant administration of 10 mg progesterone kg-1 (0.65 +/- 0.02 pg per cell). The results suggest that PHase expressed in granulosa cells may play an important role in the repair of ruptured follicle walls, via progesterone-dependent PHase production.