345 EFFECT OF FOLLICLE STIMULATING HORMONE AND HUMAN CHORIONIC GONADOTROPHIN ON THE IN VITRO MATURATION OF CANINE OOCYTES

Abstract

Growth, maturation, and ovulation of the Graafian follicle depend on appropriate patterns of secretion, sufficient concentrations, and adequate ratios of various reproductive hormones, especially follicle stimulating hormone (FSH) and luteinizing hormone (LH) (Van Tol et al. 1996 Mol. Reprod. Dev. 45, 218–224). The present study investigated the effects of FSH and human chorionic gonadotrophin (hCG) on the nuclear maturation of canine oocytes. In addition, in order to investigate the effect of stage of the estrous cycle on the meiotic competence of canine oocytes matured in vitro, oocytes were collected from various reproductive states and matured in vitro in the presence of the gonadotrophins. Estrous cycle stage was evaluated for each bitch by ovarian morphology, and bitches were categorized according to the stage of the estrous cycle (anestrus, follicular, or diestrus) prior to oocyte collection. Recovered oocytes were cultured in serum-free tissue culture medium (TCM)-199 supplemented with various concentrations of FSH (Exp. 1: 0, 0.1, 1.0, or 10 IU) or hCG (Exp. 2: 0, 0.5, 1.0, or 10 IU) or both (Exp. 3: 1 IU FSH + 1 IU hCG) for 72 h to determine the effective concentration of these hormones, and to examine their combined effect. After maturation culture, oocytes were denuded in PBS containing 0.1% (w/v) hyaluronidase by gentle pipetting. The denuded oocytes were stained with Hoechst 33342 in glycerol and the nuclear state of oocytes was evaluated under UV light. The rates of maturation to the MII stage were significantly higher (P < 0.05) when follicular-stage oocytes were supplemented with 1 IU FSH (6.2%) compared with the other FSH-supplemented groups (0.0 to 3.3%) or to the control (1.8%), or 0.1 or 10.0 IU FSH (0 to 1.2%). Significantly higher (P < 0.05) maturation rate to MII stage was observed in follicular-stage oocytes supplemented with 1.0 IU hCG (7.2%) compared with the control or other hCG-supplemented groups (0 to 1.5%). However, FSH and hCG together did not improve the nuclear maturation rate of canine oocytes (2.4%) compared with FSH (6.2%) and hCG alone (7.2%). In conclusion, FSH or hCG alone significantly increased the maturation of canine oocytes to the MII stage.

This work was supported by grant No. M1062503005-06N250300510 from KOSEF, Republic of Korea.