In vitro maturation of bovine oocytes in the presence of bovine activin A does not affect the number of embryos.

This study was carried out to investigate whether bovine recombinant activin A present during the in vitro maturation (IVM) of cumulus enclosed bovine oocytes affects the proportion of embryos that develop to the blastocyst stage. In addition, the effect of the presence of activin A during maturation and during embryo culture was studied. Therefore, bovine cumulus oocyte complexes were matured at 39 degrees C in a humidified atmosphere with 5% CO2 in air for 24 h in: (1) culture medium M199 supplemented with 10% foetal calf serum (FCS), luteinising hormone (LH) and follicle-stimulating hormone (FSH) and 10 ng ml-1 activin A; (2) M199 without FCS but supplemented with LH and FSH and 10 ng ml-1 activin A; (3) M199 without FCS, LH and FSH but supplemented with 10 ng ml-1 activin A. Cultures without activin served as controls. After IVF the embryos were cultured in M199 supplemented with 10% FCS on a monolayer of buffalo rat liver (BRL) cells. For the second part of the study, COCs were matured in vitro in M199 supplemented with LH and FSH and 10 ng ml-1 activin A, fertilized in vitro and the embryos were cultured (1) on a monolayer of BRL cells in M199 supplemented with 10% FCS and 10 ng ml-1 of activin A, and (2) in droplets of serum free BRL-conditioned medium supplemented with 10 ng ml-1 activin A. IVM in the presence of LH, FSH and 10 ng ml-1 activin A did not change the proportion of blastocysts present at Day 9 or the proportion of hatched blastocyst at Day 11. Activin present during maturation in the absence of serum and gonadotrophic hormones also did not alter the proportion of blastocysts or hatched blastocysts. In vitro culture of embryos on BRL cells or in BRL-conditioned medium in the presence of activin had no effect on embryonic development. It is concluded that IVM in the presence of bovine activin A has no effect on subsequent embryonic development.