Effect of two temperatures on in vitro nuclear maturation of bitch oocytes: relation to time culture intervals

Abstract

In the present study, two commonly incubation temperatures used on in vitro oocyte maturation in canine species (Canisfamiliaris) were analysed with the aim to verify the rate of nuclear maturation of bitch oocytes after three culture intervals (48, 72and 96 h). The culture medium was TCM 199, supplemented with 25mM Hepes/l (v/v), with 10% heat inactivated estrous cowserum (ECS), 50mg/mL gentamicin, 2.2mg/mL sodium bicarbonate and 22mg/mL pyruvic acid, 1.0mg/mL oestradiol (E 8875Sigma), 0.5mg/mL FSH (Folltropin-V, Vetrepharm Inc. Ont, Canada) and 0.03IU/mL hCG (Profasi HP, Serono, Aubonne,Switzerland). Oocytes were recovered from ovaries of bitches at random estrous cycle stages by routine ovariohysterectomy(n=14) or by therapeutical ovariohysterectomy (n=8) at the veterinary hospital of the Universidade Federal do Rio Grande do Sul(UFRGS), Brazil. There was no statistical difference in the rate of meiosis of oocytes matured at 37oC or at 39oC at any time point.However, the proportion of oocytes that reached the metaphase II (MII) stage at 37o C after 72 h of in vitro culture (16/123; 13%),tended to be higher (P=0.064), when compared to that matured at the 39oC (6/148; 4,1%). The results demonstrate thattemperatures of 37oC and 39oC are equally effective for the in vitro culture of bitch oocytes.