en 33209742 <p>Background: It is demonstrated that optimal preincubation time improves oocyte quality, fertilization potential and developmental rate. This study aimed to evaluate the effect of preincubation time in the simple and myo-inositol supplemented medium on the oocyte quality regarding oxidative stress and mitochondrial alteration.<br /> Methods: Cumulus oocyte complexes (COCs) retrieved from superovulated NMRI mice were divided in groups of 0, 4 and 8 <em>hr</em> preincubation time in the simple and 20 <em>mmol/L</em> myo-inositol supplemented media. Intracellular reactive oxygen species (H₂O₂), glutathione (GSH), mitochondrial membrane potential (MMP), ATP content, and mitochondrial amount were measured and analyzed in experimental groups. One-way ANOVA and Kruskal-Wallis were respectively used for parametric and nonparametric variables. Statistical significance was defined as p&lt;0.05.<br /> Results: In comparison to control group, variables including ROS, GSH, mitochondrial amount, fertilization and developmental rates were significantly changed after 4 <em>hr</em> of preincubation in the simple medium, while MMP decreased following 8 <em>hr</em> of preincubation in the simple medium (p˂0.001). Preincubation of oocytes up to 8 <em>hr</em> in the simple medium could not decrease ATP content. For both 4 and 8 <em>hr</em> preincubation times, myo-inositole could decrease H₂O₂ and increase GSH and MMP levels and consequently could improve fertilization rate compared to oocytes preincubated in the simple culture.<br /> Conclusion: It seems that 4 <em>hr</em> or more preincubation time can decrease the oocyte quality and lead to reduced oocyte fertilization and developmental potential. Howevere, myo-inositol may prevent oocyte quality reduction and improve fertilization potential in comparision to the equivalent simple groups.</p> Developmental rate, Fertilization potential, Mitochondrial alteration, Myo-inositol supplement, Oocyte preincubation time, Oocyte quality, Oxidative stress 259 269 https://www.jri.ir/article/120086 https://www.jri.ir/documents/fullpaper/en/120086.pdf FatemehMohammadiAnatomy Department, School of Medicine, Iran University of Medical Sciences (IUMS), Tehran, Iran112065MahnazAshrafiCellular and Molecular Research Center, Iran University of Medical Sciences (IUMS), Tehran, Iranمهناز اشرفيAshrafi.m@iums.ac.ir72ZahraZandiehCellular and Molecular Research Center, Iran University of Medical Sciences (IUMS), Tehran, IranZandieh.z@iums.ac.ir112066MohammadNajafiBiochemistry Department, School of Medicine, Iran University of Medical Sciences (IUMS), Tehran, Iran112067BehroozNiknafsAnatomy Department, School of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran322Fatemeh SadatAmjadiShahid Akbar Abadi Clinical Research Development Unit (ShACRDU), Iran University of Medical Sciences (IUMS), Tehran, Iran112068MaryamHaghighiAnatomy Department, School of Medicine, Iran University of Medical Sciences (IUMS), Tehran, Iran112069