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Nitric oxide inhibits oocyte meiotic maturation
Yasuhiko Nakamura1, Yoshiaki Yamagata, Norihiro Sugino
1Reproductive, Pediatric, and Infectious Science, Yamaguchi University School of Medicine, Ube 755-8505, Japan. yasu-ygc@umin.ac.jp
Biology of Reproduction
|October 23, 2002
Summary
Nitric oxide (NO) is crucial for oocyte maturation. The inducible nitric oxide synthase (iNOS)-NO-cGMP pathway regulates this process, with NO
Area of Science:
- Reproductive Biology
- Endocrinology
- Cell Signaling
Background:
- Nitrate/nitrite levels in preovulatory follicles decrease post-hCG injection.
- Inducible nitric oxide synthase (iNOS) is implicated in the reduction of intrafollicular nitric oxide (NO).
Purpose of the Study:
- To investigate the role of NO in oocyte meiotic maturation.
- To explore the physiological mechanisms behind the decrease in intrafollicular NO.
Main Methods:
- Immature rat ovaries were treated with eCG, followed by incubation with hCG, iNOS inhibitor (aminoguanidine), or NO donor (SNAP).
- Germinal vesicle breakdown (GVBD) and cGMP levels in follicles were assessed.
- Denuded oocytes were incubated with SNAP and hemoglobin to evaluate NO's effect on GVBD.
Main Results:
- Aminoguanidine and hCG promoted GVBD, while SNAP inhibited it.
- Aminoguanidine reduced cGMP levels, an effect reversed by SNAP.
- SNAP dose-dependently inhibited GVBD in denuded oocytes, an effect reversed by hemoglobin.
Conclusions:
- The iNOS-NO-cGMP signaling pathway plays a significant role in regulating oocyte meiotic maturation.
- NO acts as an inhibitor of GVBD, suggesting a complex regulatory role in ovulation.