Effects of L-carnitine supplemented in maturation medium on the maturation rate of swamp buffalo oocytes

In vitro maturation (IVM) is a first and crucial step to determine the success of in vitro embryo production. L-carnitine enhances lipid metabolism in cells and exerts antioxidant effects as well. Such properties are known to be beneficial for oocyte maturation. Thus, to investigate the effects of L-carnitine during IVM on maturation rate of swamp buffalo oocytes, oocytes were matured in IVM medium supplemented with 0.3, 0.6 and 1.2 mg/mL of L-carnitine (0.3, 0.6 and 1.2 L-carnitine groups, respectively). Oocytes matured in 0 mg/mL of L-carnitine were treated as a control group. After IVM, oocytes were denuded by hyaluronidase and fixed with ethanol: acetic acid (3:1) for 3 days. After that, the fixed oocytes were stained with 1% (w/v) orcein in acetic acid for 10 min. Oocytes appearing a metaphase plate and one polar body were regarded as metaphase II stage (MII). Supplementation of L-carnitine at 0.3 mg/mL (0.3 L-carnitine group) showed a significantly higher MII rate than that in control group (83/123, 67.5% vs 69/120, 57.5%); however, the rate was not significantly higher than those in 0.6 mg/mL (79/124, 63.7%) and 1.2 mg/mL (79/123, 64.2%) groups. In conclusion, supplementation of L-carnitine during IVM could improve the nuclear maturation rate to MII and 0.3 mg/mL was the optimal concentration.