Research and development in production of bovine embryos in vitro and subsequent embryo transfer

Abstract EN

The origin and the quality of the final meiotic maturation of cumulus-oocyte-complexes (COCs) in vitro are the most important factors for successful embryo production in vitro.

In this connection the cell physiological analysis of changes occurring in different parts of the COC, i.e.

in the oocyte nucleus, the ooplasm and the cumulus cells, as well as their interactions during preovulatory meiotic maturation is necessary to define the COC quality for embryo production in vitro.

We wished to investigate nuclear and cytoplasmic maturation of bovine oocytes correlated to their origin and response to prolactin treatment, by monitoring at frequent intervals meiotic configuration of chromosomes and activity of histone H1 and MAP-kinase.

Four groups of oocytes were formed: originating from small or large follicles, and treated or not treated with prolactin.

At the scheduled time intervals for in vitro maturation, cumulus oocyte complexes from the 4 groups were randomly selected and the oocytes were analyzed for histone H1 and MAP-kinase, and for chromatin configuration.

The first meiotic division took longer to complete in oocytes from large follicles (P < 0.01).

Under the influence of prolactin the meiosis was prolonged in oocytes both from small and large follicles (P < 0.05).

Histone H1 and MAP-kinases started to be activated at approximately the same time, around 6 h after beginning maturation.

But after this time, significantly lower levels of both kinase activities were found in oocytes treated with prolactin, especially those treated during Meiosis I (P < 0.05).