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Metanthiol induce relaxation of non-vascular smooth muscle in similar manner to sodium sulphide Hydrogen sulfide (H2S) has been recognized as a signaling molecule, and is rapidly emerging as an important vasoactive mediator. The effects and mechanism of its vascular activity are still unclear. It has been proposed that metanethiol (CH3SH) may represent gaseous signaling specie. Pharmacological effects of CH3SH have not been examined before and are interesting by itself. In addition, CH3SH may be very useful in studying the mechanisms of H2S signaling. In comparison to H2S, which exists as molecular H2S and anionic form HS-, CH3SH bares no charges and has a larger structural moiety but reacts with target molecules by the same functional group (thiol, -SH). Since molecular and anionic form of H2S can not be separated under conditions of our experiment, molecular CH3SH offer possibility to distinguish effects of said species. We were interested to determine the effects of exogenous CH3SH and Na2S on tone of rat uteri contractile activity [spontaneous and calcium (Ca2+)-induced], and the effect of such treatment on antioxidative enzyme activities. The rat uteri from virgin Wistar rats in oestrus were isolated following a positive vaginal test and suspended in an organ bath where vascular tone was measured and monitored using a transducer. Uteri were allowed to contract spontaneously or in the presence of Ca2+ (6 mM) and treated with Na2S and CH3SH in two separate sets of experiments, over 2 h. Anti-oxidative enzyme activities (copper-zinc superoxide dismutase-CuZnSOD, glutathione peroxidase-GSHPx and glutathione reductase-GR) in H2S -treated uteri were compared with those undergoing spontaneous or Ca2+ -induced contractions, without treatment with CH3SH/Na2S (controls 2h). Statistical analyses (descriptive statistics, analysis of variance – ANOVA) were performed according to protocols described by Hinkle et al. (1994) and Manley (1986) using Statistical Analysis Software (SAS version 9.1.3, SAS Institute, Cary, NC, USA). The effect of Na2S/CH3SH on uterine contractility was tested by two-way ANOVA (type of activation and treatment as factors) and regression analysis (the minimum level of significance was when p < 0.05). The effect of Na2S treatment on anti-oxidative defence enzymes was tested by one-way ANOVA, and the data were expressed as mean ± SEM, compared using the unequal n (number of saples) honestly significant difference post hoc test. Number of experimental animals per each experiment was between 6 and 8. CH3SH and sodium sulphide Na2S caused reversible relaxation of both spontaneous and Ca2+ -induced contractions in isolated rat uteri in tested concentration (800 μM and 200 μM, respectively) regardless the type of activation (p<0,001). Gained data demonstrate slight differences in response to CH3SH and combination of H2S and HS- indicating that their molecular form is essential for gained relaxation, and HS- specie might be responsible for difference. Opening of smooth muscle KATP channels was the principle postulated mechanism of H2S pharmacological effects, and according to our results it seems also to be the case for CH3SH. In uteri treated with CH3SH all measurements of antioxidant enzyme activity (independent of the type of activation) has followed the same pattern. CH3SH treatment led to higher SOD, GR (p< 0.001) and GSHPx (p< 0.001) activity compared to controls (C2h). Antioxidant enzyme activities from uteri treated with Na2S differ in comparison to activities from uteri treated with CH3SH. In this case SOD activity was decreased (independent of the type of activation). Higher GR and GSHx activity was found only in the case of Ca2+ active uteri compared to controls (p < 0,001). These differences between CH3SH and Na2S effects on antioxidative enzymes actvities indicate that redox effects of these two species may differ, so further examination of their pharmacological effect mechanisms is necessary which is under progress in our laboratory.
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