In an earlier study, we have demonstrated that supplementation of lysyl oxidase (LOX) has the beneficial effect on the developmental competence of both normal and metabolic stressed cumulus oocyte complexes (COCs). The present study investigated the mRNA expression of LOX in normal COCs of different grades, both immature and matured ones and in metabolic stressed matured COCs by qPCR. The effects of different concentrations (0, 10, 20, 30, 40, 50, 60 µg/ml) of β-aminopropionitrile (β-APN), a

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... -Inhibitor on in vitro maturational competence and viability rates of ovine COCs were also examined. The mRNA expression of LOX in metabolic stressed COCs supplemented with a LOX inhibitor was also examined. mRNA expression level of LOX was higher in good quality oocytes followed by fair and poor quality ones. The mRNA expression of LOX reduced when COCs were exposed to metabolic stressors. Supplementation of 50 µg/ml β-APN during IVM significantly decreased both maturational competence and viability of COCs. Lower mRNA expression of LOX in 250 µM ammonia was followed by 6 mM urea, 210 μM NEFA and 1.0 µM β-OHB. In conclusion, lysyl oxidase (LOX) can be considered as a candidate biomarker of oocyte quality and may be useful for the selection of good quality oocytes for assisted reproduction.