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

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.