The Secretion Activity of Granulosa-Cells in the Cows Ovaries in Relation to Invitro Production of Prolactin Or Prolactin-Like Substance

Veterinarni Medicina 36, 1991, 577-583

Ovarian functions are regulated by a wide variety of substances of hypothalamic, pituitary and intraovarian origin. In particular, prolactin (PRL) plays an important role in the control of ovaries. The aim of our in-vitro experiments was to prove a possibility of PRL production by bovine granulosa cells and to search into the endocrine regulators of this process. In the course of experiment 1 (Fig. 1) it was observed that the marked time-dependent accumulation of immunoreactive PRL took place during long-time cultivation of granulosa cells both in serum-free and in serum-dependent medium. After 12-24 hours of cultivation this level was reduced, but after 120 hours of cell culture the medium PRL-immunoreactivity gradually rose to exceed the starting level 2.1-2.4 times. FSH additions (10-10 000 ng/ml) led to a dramatical rise of PRL-immunoreactivity in a dose-dependent manner (Fig. 2). A greater increase in FSH doses (1000 or 10 000 ng/ml) activated this process 14.0-18.0 times. In the other experiments (Tab. I) the effects of LH, LH-RH and various nonapeptide hormones on the PRL-like substance production were investigated. LH stimulated PRL-like substance production at a great dose only (10 IU/ml). The lower doses did not have any significant influence on the process. Low doses of oxytocin (1 or 10 IU/ml) blocked, and higher doses (100-10 000 IU/ml) stimulated the granulosa PRL-like production. Arginine-8-vasopressin (AVP) (1-1000 ng/ml), arginine-8-vasotocin (AVT) (10-10 000 ng/ml), or LH-RH (10-10 000 ng/ml) failed to influence the immunoreactive PRL accumulation in the culture medium. The increase of PRL immunoreactivity after gonadotrophin additions was not due to the contamination of preparations by PRL because the serum-free medium did not contain any PRL after FSH and LH additions (but before granulosa cultivation). Thus FSH and probably LH may play a certain role in the stimulation of ovarian PRL-like secretion. Present results are the first information about ovarian production of PRL or PRL-like substance and about the involvement of LH and vasopressin in the regulation of this process. Further in-vitro and in-vivo investigations will be needed to discover the physiological role and the regulation of ovarian PRL secretion

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