The role of potassium channels and calcium in the relaxation mechanism of magnesium sulfate on the isolated rat uterus

MgSO 4 is used as a tocolytic agent. It is considered to be a calcium channel antagonist, but a different mechanism of its action might be involved. The aim of this study was to examine the contribution of calcium concentrations and potassium channels in the mechanism of MgSO 4 -mediated uterine relaxation. Isolated uteri from female Wister rats were treated with increasing MgSO 4 concentrations (0.1-30 mM). MgSO 4 induced dose-dependent inhibition of spontaneous activity. Addition of Ca 2+ (6 mM and 12 mM) stimulated uterine contractile activity and attenuated the inhibitory activity of MgSO 4 . In order to analyze the role of different subtypes of potassium channels, Ca 2+ -stimulated uteri were pretreated with glibenclamide (Glib), a selective ATP-sensitive potassium channel inhibitor (K ATP ), tetraethylammonium (TEA), a non-specific inhibitor of large conductance calcium-activated potassium channels (BK Ca ), and 4-aminopyridine (4-AP), a voltage-sensitive potassium channel inhibitor (Kv), at concentrations that had no effect per se . Pretreatment with 4-AP had no effect on MgSO 4 -mediated relaxation of Ca 2+ -stimulated uteri. The relaxing effect of MgSO 4 was potentiated by pretreatment with glibenclamide. Pretreatment with TEA attenuated the MgSO 4 -mediated decrease in frequency. Our results suggest that MgSO 4 acts as a general calcium antagonist that influences Ca 2+ -mediated potassium channels. Furthermore, it seems that MgSO 4 uterine relaxation activity is partially mediated by selective ATP-sensitive potassium channels, suggesting an ATP-dependent role. https://doi.org/10.2298/ABS180615031S Received: June 15, 2018; Revised: July 6, 2018; Accepted: July 6, 2018; Published online: July 16, 2018 How to cite this article: Sokolovic D, Drakul D, Orescanin-Dusic Z, Tatalovic N, Pecelj M, Milovanovic S, Blagojevic D. The role of potassium channels and calcium in the relaxation mechanism of magnesium sulfate on the isolated rat uterus. Arch Biol Sci. 2019;71(1):5-11.