Effects of nitric oxide synthase inhibitors on porcine oocyte meiotic maturation

Area of Science:

• Reproductive Biology
• Cell Signaling
• Biochemistry

Background:

• Nitric oxide (NO) is a key signaling molecule in various physiological and pathological processes.
• NO influences mammalian oocyte meiotic maturation.
• The roles of specific nitric oxide synthase (NOS) isoforms in porcine oocyte maturation require elucidation.

Purpose of the Study:

• To investigate the involvement of inducible NOS (iNOS) and endothelial NOS (eNOS) in porcine oocyte meiotic maturation.
• To examine the function of cumulus cells in oocyte development and degeneration.
• To differentiate the roles of iNOS and eNOS in oocyte maturation using specific inhibitors.

Main Methods:

• Porcine oocytes (cumulus-enclosed oocytes - CEOs and denuded oocytes - DOs) were cultured with NOS inhibitors.
• Cumulus expansion, cumulus cell DNA fragmentation, and oocyte meiotic resumption were assessed.
• Selective iNOS inhibitor (Aminoguanidine) and non-selective NOS inhibitors (L-NNA, L-NAME) were used.

Main Results:

• Selective iNOS inhibition (Aminoguanidine) suppressed cumulus expansion and oocyte meiotic resumption in CEOs.
• Non-selective NOS inhibition (L-NNA, L-NAME) delayed cumulus expansion, inhibited cumulus cell DNA fragmentation, and reduced meiotic resumption in CEOs.
• No significant effects of NOS inhibitors were observed in DOs.

Conclusions:

• iNOS-derived NO is essential for cumulus expansion and meiotic maturation, mediating cumulus cell function.
• eNOS-derived NO also contributes to porcine oocyte meiotic maturation.
• Cumulus cells play a critical role in oocyte maturation, influenced by NO signaling.