Nitric oxide (NO) has an important role in oocyte maturation and embryonic development in mammals. This study examined the effect of exogenous NO donor S-nitroso-N-acetylpenicillamine (SNAP) in a maturation medium on meiotic progression and embryonic development after parthenogenesis (PA) and somatic cell nuclear transfer (SCNT) in pigs. When oocytes were exposed to 0.1 μM SNAP for first 22 h of in vitro maturation (IVM) in Experiment 1, SNAP significantly improved blastocyst development in both defined and standard follicular fluid-supplemented media compared to untreated control (48.4 vs. 31.7-42.5%). SNAP treatment significantly arrested meiotic progression of oocytes at the germinal vesicle stage at 11 h of IVM (61.2 vs. 38.7%). However, there was no effect on meiotic progression at 22 h of IVM (Experiment 2). In Experiment 3, when oocytes were treated with SNAP at 0.001, 0.1 and 10 μM during the first 22 h of IVM to determine a suitable concentration, 0.1 μM SNAP (54.2%) exhibited a higher blastocyst formation than 0 and 10 μM SNAP (36.6 and 36.6%, respectively). Time-dependent effect of SNAP treatment was evaluated in Experiment 4. It was observed that SNAP treatment for the first 22 h of IVM significantly increased blastocyst formation compared to no treatment (57.1% vs. 46.2%). Antioxidant effect of SNAP was compared with that of cysteine. SNAP treatment significantly improved embryonic development to the blastocyst stage (49.1-51.5% vs. 34.4-37.5%) irrespective of the presence or absence of cysteine (Experiment 5). Moreover, SNAP significantly increased glutathione (GSH) content and inversely decreased the reactive oxygen species (ROS) level and mitochondrial oxidative activity in IVM oocytes. SNAP treatment during IVM showed a stimulating effect on in vitro development of SCNT embryos (Experiment 7). These results demonstrates that SNAP improves developmental competence of PA and SCNT embryos probably by maintaining the redox homeostasis through increasing GSH content and mitochondrial quality and decreasing ROS in IVM oocytes.

Abstract
 INTRODUCTION
 MATERIALS AND METHODS
  1. Culture media
  2. Oocyte collection and IVM
  3. Somatic cell nuclear transfer (SCNT) and parthenogenesis (PA)
  4. Post-activation and embryo culture
  5. Measurement of GSH and ROS contents
  6. Determination of mitochondrial oxidative activity in oocytes
  7. Examination of nuclear status of oocytes
  8. Experimental design
  9. Statistical analysis
 RESULTS
  1. Effects of SNAP in maturation medium with PVA or PFFon embryonic development after PA
  2. Effect of SNAP treatment on nuclear status of oocytesat 11 and 22 h of IVM
  3. Effects of SNAP treatment at various doses during IVMon embryonic development after PA
  4. Effects of SNAP treatment at various stages of IVM onembryonic development after PA
  5. SNAP treatment with or without cysteine in a chemicallydefined medium during IVM on embryonic developmentafter PA
  6. Effect of SNAP treatment on GSH content, ROS level andmitochondrial oxidative activity of oocytes after IVM
  7. Effect of SNAP treatment during 0-22 h of IVM on embryonicdevelopment after SCNT
 DISCUSSION
 REFERENCES

• Fazle Elahi(College of Veterinary Medicine, Kangwon National University)
• Hyeji Shin(College of Veterinary Medicine, Kangwon National University)
• Joohyeong Lee(Institute of Veterinary Science, Kangwon National University)
• Seung Tae Lee(Division of Applied Animal Science, College of Animal Life Science, Kangwon National, University)
• Geun-Shik Lee(College of Veterinary Medicine, Kangwon National University, Institute of Veterinary Science, Kangwon National University)
• Eunsong Lee(College of Veterinary Medicine, Kangwon National University, Institute of Veterinary Science, Kangwon National University) Correspondence