[Realization pathways of prolactin modulating influence on the cAMP-dependent mechanism of meiosis regulation in bovine oocytes].

Cyclic AMP is one of the key regulators of mammalian meiosis. In the present work, realization pathways of the previously revealed modulating influence of prolactin (PRL) on the cAMP-dependent mechanisms of meiosis regulation in bovine oocytes were studied. A comparative investigation of individual and combined effects of PRL (50 ng/ml) and an activator of adenylate cyclase forskolin (FK. 20 microM) on the meiotic reinitiation and nuclear maturation completion in cumulus-enclosed and cumulus-free oocytes was performed. It has been shown that the pattern of PRL influence on the meiotic resumption in oocytes devoid of cumulus cells depends on the presence of FK in the culture medium. Furthermore, realization of this influence is not associated with the activation of cytoplasmic isoforms of protein kinase C. It has been also found that PRL inhibits the retarding action of FK on the completion of oocyte nuclear maturation in both the presence and absence of cumulus cells. The findings suggest that PRL may modulate the functioning of the cAMP-dependent mechanism of meiosis regulation by the direct action on bovine oocytes, with realization of the action being independent of the metabolic coupling of oocytes with cumulus cells.

[Interaction of signal cascades induced by cAMP and prolactin in bovine oocyte-cumulus complexes].

Prolactin (PRL) is one of the pituitary hormones participating in the control of mammalian folliculo- and oogenesis. In the present study, the joint effect of PRL (50 ng/ml) and dibutyryl cAMP (dbcAMP, 1 mM) on oocyte maturation and the morphologic-functional state of surrounding cumulus cells was investigated in vitro. It has been shown that PRL totally suppresses the braking impact of dbcAMP on meiosis reinitiation and the completion of oocyte nuclear maturation. Furthermore, PRL partly inhibited cumulus expansion induced by dbcAMP, although it exerted the opposite effect in the control medium. In the presence of PRL, the inhibitory impact of dbcAMP on the proliferative activity of cumulus cells and on the PRL-elicited braking of destructive processes in the cells has been found. In cumulus cells, mRNA expression of PRL receptor long isoform was revealed by the RT-PCR method. The data obtained suggest an interaction of signal cascades induced by PRL and cAMP in bovine oocyte-cumulus complexes, with the coupling site of these cascades in oocytes being apparently different from that in cumulus cells.

The effect of arginine-vasotocin on the production of steroid hormones by mouse, cow, and chicken ovarian tissues in vitro.

The effect of arginine-vasotocin (50 ng ml-1) on the in vitro production of progesterone, testosterone, and oestradiol by isolated cow and chicken ovarian follicles and mouse ovaries was studied. This peptide (1) enhanced the release of progesterone into the medium by the ovarian tissues of all three species of animal; (2) inhibited the production of oestradiol by mouse and cow ovaries; (3) had no significant effect on testosterone secretion in any of the species studied. The results obtained indicate that arginine-vasotocin directly influences steroid production in mammalian and avian gonads.

[Release of steroid hormones in vitro by ovarian follicles of various degrees of maturity in hens and cows]. / Vydelenie steroidnykh gormonov in vitro ovarial'nymi follikulami raznoi stepeni zrelosti u kur i korov.

The growth of ovary follicules was accompanied by a considerable decrease in the secretion of progesterone, testosterone and estradiol, as well as by a decrease of the estradiol share in total hormone production,--both in hens and in cows. The hens also revealed a decrease of the testosterone share and an increase of the progesterone share in total hormone production. the data obtained suggest a functional atresia of the ovary follicules in hens as well as in mammals. the hen mature follicules, however, differ from those of mammals in that the progesterone secretion is higher in them as compared with other steroids, the progesterone being the main ovulatory hormone in birds.