In vitro maturation, in vitro fertilization and embryo culture in equine are extremely important and necessaries for examining reproductive problems in the mare. The aim of the present study was to determine the effect of gonadotropins on nuclear maturation of equine oocytes. Follicles-smaller than 20mm were aspirated from 551 ovaries obtained at slaughterhouse, 408 oocytes suitable for culture being recovered. After aspiration, oocytes were evaluated in follicular fluid and distributed in four treatments. In the first treatment, control group, oocytes (n=92) were cultured for 24 hours in modifled TCM-199 with 25mM HEPES, 2.2mg/ml sodium bicarbonate, 1mug/ml 17 beta estradiol, 250mu M piruvic acid and 0.4% bovino serum albumin. In the second treatment, oocytes (n=108) were cultured in modified TC M-199 plus 1mu g/ml porcine LH. In the third treatment, 102 oocytes were cultured in modifled TCM-199 with the addition of 0.5mu g/ml porcino FSH and on the fourth treatment oocytes (n=106) were cultured in modifled TC M-199 with 1mu g/ml porcine LH and 0.5mug/ml porcine FSH. All four groups were cultured for 24h in an atmosphere with 5% CO2 at 39°C. Afterwards, cumulus cells were removed and oocytes were fixed in acetic acid-methanol (1:3) solution for 24h and stained with aceto-orcein. A significantly greater percentage of MII was observed in oocytes cultured with FSH/LH 59/106 (55.6%) and with FSH 55/102 (53,9%) than in the other groups. When oocytes were cultured in the presence of porcine LH, only 35/108 (32,4%) reached the MII stage, a similar percentage being obtained with the control group. This results demonstrate that equine oocytes cultured in vitro are stimulated to reach metaphase II when they are cultured in the presence of porcine FSH alone or added with porcine LH. Otherwise, porcine LH alone does not stimulate nuclear maturation beyond that obtained with oocytes cultured in the absence of gonadotropins.
oocyte; equine; gonadotropins
