RESUMO
The present study was undertaken to compare the efficacies of Cryotop (CT), solid surface vitrification (SSV) methods and cytochalasin B (CB) treatment for the cryopreservation of immature bovine oocytes, in terms of survival, nuclear maturation, and in vitro development. Solution exposed oocytes were in vitro maturated and fertilized. No difference was found in the rates of survival, nuclear maturation and blastocyst among solution exposed groups and fresh control group, except blastocysts rates in oocytes exposed to CB, cryoprotectant (CPA) and fluorescein diacetate (FDA) group (CB-CPA-FDA) (23%) significantly lower than that of control group (32%). CB pretreated ((+)CB) or non-pretreated ((-)CB) COCs were vitrified either by SSV or CT. Among four vitrified groups the nuclear maturation rates (CT(-)CB: 58%, CT(+)CB: 57%, SSV(-)CB: 60%, SSV(+)CB: 63%), cleavage (CT(-)CB: 36%, CT(+)CB: 24%, SSV(-)CB: 34%, SSV(+)CB: 26%) and blastocysts rates (CT(-)CB: 6%, CT(+)CB: 7%, SSV(-)CB: 4%, SSV(+)CB: 6%) did not differ, but the rates of the four vitrified groups were significantly lower than those of non-vitrified group (81%, 71% and 26%, respectively). We thus conclude that CT and SSV perform equally in vitrification of bovine immature oocytes, and CB did not increase the viability, nuclear maturation, or in vitro development of vitrified oocytes.
Assuntos
Bovinos/fisiologia , Criopreservação/veterinária , Crioprotetores/metabolismo , Citocalasina B/metabolismo , Oócitos/citologia , Vitrificação , Animais , Blastocisto/citologia , Sobrevivência Celular , Criopreservação/métodos , Desenvolvimento Embrionário , Feminino , Fertilização in vitro/métodos , Fertilização in vitro/veterinária , Técnicas de Maturação in Vitro de Oócitos/métodos , Técnicas de Maturação in Vitro de Oócitos/veterinária , Masculino , Oócitos/efeitos dos fármacos , Oócitos/metabolismoRESUMO
In this study, the effects of the addition of L-carnitine in in vitro maturation (IVM) medium for bovine oocytes on their nuclear maturation and cryopreservation were investigated; they were matured in IVM medium supplemented with 0.0, 0.3, 0.6 and 1.2 mg/mL of L-carnitine (control, 0.3, 0.6 and 1.2 groups, respectively) and some of them were vitrified by Cryotop. Moreover, the effects of L-carnitine during in vitro fertilization (IVF) and in vitro culture (IVC) on the developmental potential and quality of IVF embryos were also examined. A significantly higher maturation rate of oocytes was obtained for 0.3 and 0.6 mg/mL groups compared with the control (P < 0.05). The blastocyst formation rate in the 0.6 group was significantly improved, whereas the rate in the 1.2 group was significantly decreased when compared with the control group (P < 0.05). No significant difference was found in embryo development between the control and the L-carnitine group after oocyte vitrification. Supplementation of IVF and IVC media with L-carnitine had no effect on development to the blastocyst stage of IVM oocytes treated with 0.6 mg/mL L-carnitine. In conclusion, the supplementation of L-carnitine during IVM of bovine oocytes improved their nuclear maturation and subsequent embryo development after IVF, but when they were vitrified the improving effects were neutralized.