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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
PubMed

Insights

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.

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