Efeito do resfriamento na ploidia de ovócitos bovinos maturados in vitro

Abstract

The present study aimed to verify the incidence of bovine diploid oocytes when cooled at various maturation stages. Bovine cumulus-oocyte complexes were recovered from ovaries at a local slaughterhouse and divided into five groups: control group (uncooled oocytes), 0/4 h group (oocytes cooled at 4oC before the onset of maturation), 0/29 (composed of oocytes cooled at 29oC before the onset of maturation), 12/4 (cooled 12 h at 4oC after the onset of maturation), and 12/29 h group (cooled 12 h at 29oC after the onset of maturation). the oocytes remained cooled for 45 min. in all groups, the oocytes completed 24 h maturation. Subsequently, the cumulus cells were removed, and the denuded oocytes fixed on slides and stained with aceto-orcein. No differences (P > 0.05) in the incidence of diploid metaphase ii oocytes were observed between the control group (6.0%) and oocytes cooled at 4oC and 29oC before (8.9% and 8.0%) and after 12 h the onset of maturation (3.9% and 0.0%). These results suggest that the nuclear stage at which bovine oocytes are cooled does not affect the incidence of diploid oocytes after 24 h maturation. Key-Words: Bovine, cooling, diploid, in vitro maturation, oocytes.