Endocrine Abstracts

Introduction: VPA, antiepileptic drug, may cause a number of side effects including reproductive deficits in humans. Previously we found that VPA (1 μM) may suppress GnRH-stimulated release of LH from rat anterior pituitary cells in vitro without affecting its basal secretion (Neuroendocrinol Lett 2011 32 101–106). However mechanism of VPA suppressive activity is still unknown. Since pharmacological effects of VPA require GnRH-R activation, the mechanism of its action might occur via modulation of IP₃/PKC pathway activity.

Aim: The aim of this study was to evaluate: firstly – an effect of VPA on phorbol ester -PKC activator (TPA) -induced LH release, secondly – an effect of VPA treatment on IP₃ synthesis in the primary culture of female rat anterior pituitary cells.

Material and methods: Dispersed cells (5×10⁵/ml) were incubated for 3 h with TPA (100 nM), VPA (10 nM–10 μM) or both (TPA+VPA). As controls, incubations with GnRH (100 nM) as well as GnRH+VPA (1–10 μM) were prepared. In the second experiment cells were preincubated (37°C) for 24 h with 1 μCi myo-[2³ H]-inositol, then for 30 min with 10 mM LiCl and finally for 3 h in the presence of GnRH (100 nM), VPA (100 nM, 1 μM) or both (100 nM GnRH+100 nM or 1 μM VPA). Medium rLH concentration were estimated by RIA method, cellular IP₃ concentrations were estimated by ion-exchange chromatography analysis.

Results: VPA administration did not affect TPA-induced LH release from anterior pituitary cells at any VPA dose tested. VPA treatment resulted in a dose independent significant increase of IP₃ cellular concentrations. Moreover, VPA-induced IP₃ synthesis reached the same level as was detected after GnRH stimulation.

Conclusions: Obtained data suggest that the inhibitory effect of VPA on GnRH-stimulated LH release is not exerted via down-regulation of IP₃/PKC pathway activity.

This study was supported by CMKP grants 501-1-31-45-10 and 502-1-31-01-11.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.