Effect of indomethacin on ovarian follicle rupture--a morphological observation

The purpose of this investigation was to study the role played by indomethacin in blocking ovulation. Immature Wistar rats induced to maturation by PMSG and HCG and normal mature rats were used. Changes in follicle wall of preovulatory follicles occurred after indomethacin treatment were studied both by light and electron microscopy, and were compared with those in controls. 94% of PMSG and HCG stimulated rats, then followed indomethacin injection (3 mg/rat), were inhibited to ovulate; while rats only given hormonal stimulation ovulated in 100%. Adult females in proestrus were treated with indomethacin in doses either of 5 mg or 7.5 mg, none of them ovulated. Whereas, ova were found in the ampullae of normal controls. Ovarian histological examinations of indomethacin treated rats showed that ovum frequently went through the stratum granulosa, however, the theca or the albuginea failed to rupture. The electron microscopy examinations showed that a large amount of collagen fibers scattered under the albuginea layer and interwove with cells of albuginea and theca externa. These two layers, due to containing abundant collagen fibers, thus became barriers for an ovum escaping from a follicle. Follicle walls near the gap of ovulated follicles in controls only had a small quantity of collagen fibers which were more or less with obscure appearance. Cytolysis in albuginea and theca externa layers was also noted. Theca interna cells and granulosa cells, with well developed Golgi bodies and more smooth endoplasmic reticulum in experimental rats revealed that these two tissue components still had a normal endocrine function in spite of receiving indomethacin treatment. The possible effects of prostaglandins on degradation of collagen fibers and contraction of preovulatory follicles were also discussed.