[Effects of hydrogen sulfide on ouabain-induced delayed after-depolarization and triggered activity in guinea pig papillary muscles].

OBJECTIVE

To explore the effects of hydrogen sulfide (H(2)S) on delayed after-depolarization (DAD) and triggered activity induced by ouabain in male guinea pig papillary muscles and to elucidate the underlying mechanisms.

METHODS

An intracellular microelectrode was used to record the patterns of DAD and triggered activity by K-H solution containing ouabain and a high concentration of calcium ion. The latent period, amplitude, duration of DAD and incidence of triggered activity were observed under a pre-treatment with different concentrations of NaHS (donor of H(2)S). The effects of glibenclamide, Bay K8644 and NG-nitro-L-arginine methyl ester (L-NAME) pretreatment on the actions of H(2)S were also studied.

RESULTS

NaHS (100, 200 µmol/L) prolonged the latent period of DAD from (12.0 ± 1.0) min to (19.9 ± 1.6) min (P < 0.05), (23.7 ± 1.3) min (P < 0.01), decreased the altitude of DAD from (11.47 ± 0.74) mV to (6.47 ± 0.33) mV, (5.65 ± 0.26) mV (both P < 0.01), shortened the duration of DAD from (205 ± 11) ms to (173 ± 10) ms and (134 ± 7) ms (both P < 0.05). The occurrence of triggered activity was inhibited from 5 samples to 4, 2 and 1 sample in 6 samples. A pretreatment of adenosine triphosphate (ATP)-sensitive potassium channel (K(ATP)) blocker glibenclamide partially blocked the preventive effects of H(2)S on ouabain-induced DAD and triggered activity. The effects of H(2)S were completely blocked by L-type calcium channel agonist Bay K8644 (0.25 µmol/L). However a pretreatment of L-NAME (1 mmol/L), a nitric oxide (NO) synthase inhibitor, showed no effects on H(2)S.

CONCLUSION

H(2)S inhibits the ouabain-induced DAD and triggered activity in guinea pig papillary muscles. The opening of K(ATP) channel with a reduced influx of calcium ion may be involved in the protective effects of H(2)S.