engleski

Interaction of activin-A with various secretogogues on secretion and cell content of FSH, LH, GH, and PRL by ovine pituitary cells in culture

Background and purpose: Activins as members of the transforming growth factor beta family of gene products are dimeric proteins isolated from follicular and testicular fluids and consists of two subunits linked by interchain disulfide bridges. They selectively stimulate pituitary cells in culture to secrete FSH, but not LH. The aim of this research was to find out whether activin-A in regulating pituitary function beside regulation of FSH secretion may exert effects on synthesis and release of other pituitary hormones. Material and methods: Influence of Activin-A (1x10-8 M) on pituitary hormone synthesis and their secretion was followed by pituitary primary cell culture technique (0.3 - 0.5x106 cells/well) . Anterior pituitary glands, taken aseptically from mature ewes were source for pituitary cells. Pituitary hormones were assayed by double antibody RIA technique at incubation medium and in the plated cells. Ovine pituitary cells were cultured in vitro to determine the interaction of activin-A with various compounds known to either stimulate or suppress secretion of follicle stimulating hormone (FSH), luteinizing hormone (LH), growth hormone (GH) and prolactin (PRL). Stimulators of hormone secretion were gonadotropin-releasing hormone (GnRH), growth hormone releasing factor (GHRF) or thyrotropin releasing hormone (TRH), each at 10 nM. Suppressors of hormone secretion were bovine follicular fluid (bFF) (1 mL), somatotropin release inhibiting factor (SRIF) 10 nM or bromocriptine 10 nM. Results: Activin-A significantly (P< 0, 05) stimulated, during 18 hr incubation preconditioned pituitary cells, secretion of only FSH into medium but not other pituitary hormones. Influence of activin-A on LH secretion into medium under the influence of GnRH was not significantly different, but it reduced content of LH in non-activin-A pretreated cells. GHRH increased while SRIF or bromocriptine reduced secretion of GH into medium, either with or without activin-A pretreatment. Strong inhibitory effect of GHRH and SRIF are present on GH content in cells, while in activin-A treated or non-pretreated cells GH content was not influenced by Bromocriptine treatment. Conclusions: Activin-A appeared to attenuate the effects of many secretogogues on the content of hormones in cells and reduced variation among wells. These results show that the action of activin-A on ovine pituitary cells in culture is primarily to stimulate secretion of FSH.

activin-A; pituitary hormones; cell culture; ewe pituitary

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