Background: The use of C-type natriuretic peptide (CNP) combined with cysteamine during pre-maturation (IVM) can help establish a highly effective pre-IVM program. bovine oocyte developmental competence through pre-IVM with CNP coupled with cysteamine may be linked with an elevated antioxidant protection. Therefore, this approach may be an excellent option for building a pre-IVM system. matured bovine oocytes is certainly compromised compared to that of their counterparts, which might be simply due to inadequate cytoplasmic maturity (Rizos et al., 2002 ?; Sutton et al., 2003 ?). To boost the developmental competence of matured bovine oocytes, intensive studies have centered on the introduction of oocyte maturation (IVM) lifestyle systems using different pharmacological cyclic adenosine monophosphate (cAMP) modulators (Sato et al., 1990 ?; Guixue et al., 2001 ?; Mayes et al., 2002 ?; Albuz et al., 2010 ?; Zeng et al., 2014 ?; Farghaly et al., 2015 ?). Notably, latest studies show that C-type natriuretic peptide (CNP; also called NPPC), could briefly maintain the meiotic arrest of bovine oocytes cultured for 6-8 h through sustaining enough degrees of cAMP (Franciosi et al., 2014 ?; Soto-Heras et al., 2019 ?). Furthermore, pre-IVM with 100 nM CNP for 6 h elevated the amount of cells per blastocyst weighed against standard IVM EGFR-IN-3 process (no pre-IVM), recommending that CNP being a cAMP modulator during pre-IVM culture exerts positive effects on oocyte developmental competence (Franciosi et al., 2014 ?). A recent study has also showed that pre-IVM using cAMP modulator [forskolin (FSK) + non-specific phosphodiesterase (PDE) inhibitor 3-isobutyl-1-methylxanthine (IBMX)] delays meiotic EGFR-IN-3 resumption, and EGFR-IN-3 facilitates EGFR-IN-3 cumulus cell (CCs) transfer and accumulation of glutathione (GSH) within the oocyte during pre-IVM and IVM (Li et al., 2016 ?). However, whether pre-IVM treatment with CNP leads to increased GSH accumulation in the bovine oocyte remains unclear. Previous studies have shown that GSH synthesis can be stimulated by the addition of low-molecular-weight thiol compounds during the IVM of oocytes (Takahashi et al., 1993 ?; de Matos et al., 2000 ?; Zhou et al., 2008 ?). Cysteamine is usually a low-molecular-weight thiol that increases the intra-oocyte GSH levels and enhances oocyte developmental competence in different species when present during IVM (Grupen et al., 1995 ?; de Matos et al., 2002 ?; Izumi et al., 2013 ?). Additionally, previous studies with adult bovine oocytes have shown Rabbit Polyclonal to Nuclear Receptor NR4A1 (phospho-Ser351) that this addition of 100 M cysteamine to the culture medium during IVM significantly improves the percentage of the embryos development to the blastocyst stage compared to the control group (de Matos et al., 2002 ?; Merton et al., 2013 ?). However, it is unknown whether the presence of cysteamine can accelerate GSH accumulation in bovine oocytes during pre-IVM with CNP and thus enhance the developmental competence of oocyte. The purpose EGFR-IN-3 of the present study was to investigate whether pre-IVM with 100 nM CNP alone or in combination with 100 M cysteamine can promote the accumulation of GSH in bovine oocytes and exert a positive effect on oocyte developmental competence. Materials and Methods The protocols for the animal studies were approved by the Laboratory Animal Resource Center of Inner Mongolia University for the Nationalities and the study was conducted in accordance with the Animal Care and Use Statute of China. Unless otherwise stated, all chemicals were purchased from Sigma-Aldrich (St. Louis, MO, USA). Cumulus-oocyte complex ( COC) collection Ovaries belonged to a random pool of Holstein pluriparous dairy cows slaughtered in a local abattoir at the end of their economic life. These abattoir-obtained ovaries were transported to the laboratory within 2 h in sterilized saline at 26-28C. Cumulus-oocyte complexes (COCs) were aspirated with a 10 ml syringe from the antral follicles 3-6 mm in diameter. After examination under a stereomicroscope (Olympus SZ40, Tokyo, Japan), only COCs with a homogeneous cytoplasm and compact multi-layered CCs were selected, and washed three times.