Meiotic Competence and DNA Damage of Porcine Oocytes from Ovaries Exposed to an Elevated Temperature

The present study was conducted to investigate the effects of the exposure length of ovaries to an elevated temperature (41 degrees C) on the meiotic competence and DNA damage of oocytes. Ovaries were stored in physiological saline at 41 degrees C for 0 h (control), 0.5, 1.0 and 1.5 h. After exposure of ovaries to the elevated temperature, oocytes were collected and then cultured for 44 h. The length of exposure of ovaries to 41 degrees C had no effect on the proportions of total oocytes with DNA-fragmented nuclei before maturation culture, but it did influence the proportions at the end of maturation culture. The proportion of oocytes reaching metaphase II (MII) significantly decreased with increasing exposure time. In addition, significantly more oocytes from ovaries exposed to 41 degrees C for 1.5 h had DNA-fragmented nuclei compared with control oocytes. These results indicate that the meiotic competence and DNA damage of porcine oocytes are dependent on the duration of exposure of ovaries to the elevated temperature. Moreover, the occurrence of DNA damage in oocytes becomes more apparent after maturation culture than before the culture.