To explore the effects of hydrogen sulfide (H₂S) on colonic contraction of rats at low concentration and ion channel mechanisms.
Organ bath recordings were used to examine the contraction of colonic smooth muscle strips. The whole-cell patch-clamp technique was used to record the currents of L-type calcium and large conductance Ca²⁺-activated K⁺ (BKCa) channels in smooth muscle cells isolated from 30 male Wistar rats.
The H₂S donor NaHS ((1-12) × 10⁻⁵ mol/L) increased the spontaneous contractions of longitudinal and circular muscle strips in a dose-dependent manner (all P<0.05) and the effect could not be blocked by tetrodotoxin. NaHS (6 × 10⁻⁵ and 12 × 10⁻⁵ mol/L) reversibly increased the L-type calcium current (ICa,L) in a dose-dependent manner. And the peak of ICa,L at 0 mV increased from (-3.16 ± 0.47) to (-3.33 ± 0.54) and (-3.65 ± 0.66) pA/pF respectively (n=6, both P<0.05). Current-voltage (I-V) curve had no shift after NaHS treatment and H₂S donor caused no change in the curves of steady-state activation. Likewise BKCa channel was significantly inhibited by NaHS (6 × 10⁻⁵ and 12 × 10⁻⁵ mol/L) in a dose-dependent manner. And IBKCa at 60 mV decreased from (16.68 ± 1.23) to (15.26 ± 2.67) and (13.80 ± 3.04) pA/pF respectively(both P<0.05).
H2S at low concentrations increases the spontaneous contraction of rat colonic smooth muscle in a dose-dependent manner. Such an effect may be due to a direct activation of L-type calcium channel and an inhibition of BKCa channel in smooth muscle cells.
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