Reactive oxygen species in bovine oocyte in vitro maturation

SERGIO MORADO; PABLO CETICA; MARTHA BECONI; GABRIEL DALVIT

Buenos Aires (Argentina)

Jornada; VII Jornadas Multidisciplinarias de la Sociedad Argentina de Biología; 2005

Sociedad Argentina de Biología

REACTIVE OXYGEN SPECIES IN BOVINE OOCYTE IN VITRO MATURATION Morado S., Cetica P., Beconi M. and Dalvit G. Química Biológica, Facultad de Ciencias Veterinarias, Universidad de Buenos Aires. smorado@fvet.uba.ar   Oxidative modifications of cell components due to the action of reactive oxygen species (ROS) is one of the most potentially damaging processes for proper cell function; however, in the last few years it has been observed that ROS participate in physiological events. The aim of this work was to determine the possible variation of ROS production throughout bovine oocyte in vitro maturation. Cumulus-oocyte complexes were recovered by aspiration of antral follicles from ovaries obtained from slaughtered cows and cultured in medium 199 with or without cysteine 0.6 mM at 39ºC, 5% CO2 in humidified air for 22 h. ROS production was determined in denuded oocytes each 2-h interval (0-22 h) calculating the ratio between the 2´,7´-dichlorodihydrofluorescein diacetate (DCHFDA) and fluorescein diacetate (FDA) fluorescent assays by the analysis of digital microphotographs. Meiotic maturation determined by the presence of the metaphase II chromosome configuration was 87%. At 18 h of maturation, 80% of the analyzed oocytes showed first polar body. ROS levels expressed as DCHFDA/FDA ratio fluctuated throughout the 22 h of bovine oocyte in vitro maturation, showing a significant decrease at 6 h and 18 h from the start of culture period (P<0.05). Oocytes matured in the presence of cysteine showed a decrease in ROS production (P<0.05). No significant differences were observed in esterase activity during in vitro maturation (FDA). In this study, the variation in ROS level during the complete process of oocyte in vitro maturation was determined for the first time in a mammalian species. During bovine oocyte in vitro maturation an important variation in ROS production takes place, decreasing in coincidence with the germinal vesicle breakdown and the polar body emission.