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

In this study we investigated the role of voltage dependent (K V ), Ca 2+ -activated (K Ca ), and inward rectifier (K ir ) potassium channels in the effects of hydrogen sulfide donor (H 2 S) 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 (EC 50 ) of the inhibitory effect of NaHS on the amplitude of contractions was 165 μM. The blocker of K V 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 K Ca 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 K Ca 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 K ATP 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 K ATP channel blocker glibenclamide (50 μM) prevented the effect of NaHS on the tonus of the preparation. BaCl 2 , the K ir 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 H 2 S donor was associated with activation of K ir channels, including K ATP channels, whereas the effect of H 2 S on amplitude and frequency was mediated by an increase in Ba 2+ -sensitive conductivity.