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4. Effect of Hydrogen Sulphide on Spontaneous Contractions of the Rat Jejunum: Role of KV, KCa, and Kir Channels.

Author

Sorokina, D. M., Shaidullov, I. F., Buchareb, D., Sitdikov, F. G., and Sitdikova, G. F.

Abstract

In this study we investigated the role of voltage dependent (KV), Ca2+-activated (KCa), and inward rectifier (Kir) potassium channels in the effects of hydrogen sulfide donor (H2S) sodium hydrosulfide (NaHS) on spontaneous contractile activity of rat jejunum. It was shown that NaHS dose-dependently (10–500 μM) reduced the tonus of the preparation, as well as the amplitude and frequency of spontaneous contractions of jejunum preparations under isometric conditions; the half-maximal effective concentration (EC50) of the inhibitory effect of NaHS on the amplitude of contractions was 165 μM. The blocker of KV channels 4-AP (200 μM) caused an increase in the amplitude of spontaneous contractions. NaHS (200 μM) decreased the amplitude and frequency of spontaneous activity of the preparation in the presence of 4-AP as well as in the control, and the effect on basal tonus was less pronounced. Blockers of large conductance KCa channels (BK), non-specific TEA (3 mM) and specific paxillin (1 μM), increased the amplitude of spontaneous contractions, while the depressing effect of NaHS was completely preserved. The selective blocker of small conductance KCa channels (SK) NS8593 (4 μM) did not affect the tonus of the preparation and the parameters of spontaneous contractions; it did not prevent the effect of NaHS. The activator of KATP channels diazoxide (100 μM) caused a decrease in the basal tonus of the preparation, as well as the amplitude and frequency of spontaneous contractions. Diazoxide and the KATP channel blocker glibenclamide (50 μM) prevented the effect of NaHS on the tonus of the preparation. BaCl2, the Kir channel blocker (30 μM), caused an increase in the amplitude of spontaneous contractions and prevented the development of the NaHS inhibitory effects on the frequency and amplitude of spontaneous contractions; the decrease in tonus was less pronounced than in the control. Thus, a decrease in the basal tonus of the rat jejunum preparation under the action of the H2S donor was associated with activation of Kir channels, including KATP channels, whereas the effect of H2S on amplitude and frequency was mediated by an increase in Ba2+-sensitive conductivity. [ABSTRACT FROM AUTHOR]

Published
2023
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7. The Roles of Nitric Oxide and Calcium Ions in the Effects of Hydrogen Sulfide on the Contractile Activity of the Rat Jejunum.

Author

Sorokina, D. M., Shaidullov, I. F., Gizzatullin, A. R., Sitdikov, F. G., and Sitdikova, G. F.

Abstract

The roles of nitric oxide, intra- and extracellular calcium in the effects of hydrogen sulfide on spontaneous and carbachol-induced contractions of rat jejunal preparation under conditions of isometric contraction were studied. A donor of H2S (sodium hydrosulfide) led to a decrease in the preparation tone, amplitude and frequency of spontaneous contractions, as well as parameters of the contractions caused by carbachol, a nonspecific agonist of acetylcholine receptors. The effect of the H2S donor persisted under conditions of the inhibition of endogenous NO synthesis with L-NAME, while in the presence of the action of SNAP (an NO donor), the effects of NaHS on the amplitudes of spontaneous and carbachol-induced contractions were less pronounced. A decrease in preparation tone under the effect of NaHS was prevented by dantrolene, a blocker of ryanodine receptors. The calcium-free solution decreased the inhibitory effect of NaHS on the contractions induced by the application of carbachol. It is suggested that the inhibitory effect of H2S is associated with the dynamics of intracellular concentration of calcium ions, and the interaction of NO and H2S occurs at the level of common targets of the effect of the two gases. [ABSTRACT FROM AUTHOR]

Published
2023
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