Resistance of bovine oocytes to age-related changes after exposure to luteotropic factors during the second phase of culture till the metaphase II stage

After the completion of the first division of meiosis in oocytes of various mammalian species, including cattle, the aging processes are acutely activated, which adversely affects the quality of mature ova and their competence to embryonic development after fertilization. Endogenous progesterone (P4) is known to play an important role in maintaining the viability of bovine oocytes, with its production by surrounding cumulus cells increasing significantly in the course of the final maturation period of female gametes from metaphase I to metaphase II (MII). However, effects of P4 and its two main stimulators, prolactin (PRL) and luteinizing hormone (LH), during maturation of oocytes on their resistance to age-related transformations are still poorly studied. We performed for the first time a comparative investigation of abnormal changes of MII chromosomes and apoptotic degeneration of oocytes, ripened by exposure to P4, PRL, and LH in the absence and in the presence of granulosa cells, during the subsequent prolonged culture of the ova...