CRIOTOLERANCIA DE EMBRIONES BOVINOS CULTIVADOS INDIVIDUALMENTE EN UN MEDIO SUPLEMENTADO CON L-CARNITINA

Background: L-carnitine is a lipid metabolism enhancer and a potent antioxidant that prevents oxidative damage and improves cryotolerance of bovine embryos. Objective: To determine the effect of L-carnitine during oocyte maturation on developmental competence and cryotolerance of single bovine embryo cultured. Methodology: Embryos were produced in vitro using abattoir-derived cumulus-oocyte complexes (COCs). In experiment 1, two individual maturation, fertilization and culture systems were used in 24-well plates with 20 µL drops of medium covered with mineral oil and 96-well plates with 30 µL drops of medium. In experiment 2, oocytes were randomly distributed into two groups and single matured in 96-well plates in medium supplemented or not with 0.6mg/mL L-carnitine. On day 7 post fertilization, blastocysts were vitrified on solid surface in Fiberplug. Non-vitrified blastocysts were used as control. Embryonic survival after devitrification was determined by blastocysts re-expansion and hatching rate at 24 and 48 hours of post-devitrification culture. Total cell number and apoptotic rate by TUNEL-DAPI staining were used as quality and cryotolerance indicator. In both cases, cleavage and blastocyst rates were evaluated at 48 hours and 7 days post fertilization, respectively. Results: No significant differences were found for embryonic development between single culture systems. There was no effect of L-carnitine supplementation during maturation on embryo development, but embryo survival had increased (P < 0.05) at 24- and 48-hours post devitrification. Implications: Treatment with L-carnitine had increased (P < 0.05) post-thaw re-expansion rates (86.8 ± 3.0 vs 70.0 ± 4.4) and it was similar to non-vitrified control (89.7 ± 2.6). Mean cell number and apoptotic cell index, were similar for all treatment groups. Conclusion: L-carnitine supplementation during maturation, does not improve division rate and subsequent development of single cultured embryos, however increases cryotolerance post devitrification.