Glutathione content and antioxidant enzyme expression of in vivo matured sheep oocytes

Retinoids play important roles in many diverse biological functions such as cell growth, morphogenesis, differentiation, and reproduction. Previous studies demonstrated that retinol administration to ewes, followed by natural service, resulted in embryos with improved competence to develop under standard in vitro conditions (5% CO2 in air). Additional studies provided evidence that retinol may have some antioxidant effect by improving blastocyst development in cattle under atmospheric conditions (5% CO2 in air). Glutathione is an important non-protein, sulphydryl compound found in oocytes and embryos, which acts to decrease oxidative stress. The purpose of the present study was to evaluate the effects of retinol administration to ewes on the content of glutathione and glutathione-related and antioxidant enzymes in in vivo matured sheep oocytes. Briefly, ewes were administered retinol or vehicle during superovulation, and after 60 h the oviducts were removed and mature oocytes collected. Glutathione content did not differ significantly between oocytes collected from retinol-treated ewes (6.78 ± 3.81 pmol/oocyte) and control ewes (6.38 ± 1.58 pmol/oocyte). Transcripts encoding for manganese superoxide dismutase (Mn-SOD), copper zinc superoxide dismutase (Cu–Zn SOD), glutathione synthetase (GS), and glutathione transferase pi (GSTp) were detected in single ovine oocytes; however, semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) analysis did not reveal any significant differences in transcripts between oocytes from retinol-treated ewes and those from control ewes.