Electrophysiological effects of hydrogen sulfide on pacemaker cells in sinoatrial nodes of rabbits.

ABSTRACT

The cardiac electrophysiological effects of hydrogen sulfide (H(2)S) on pacemaker cells in sinoatrial (SA) nodes of rabbits were examined using intracellular microelectrode technique. The results obtained were as follows (1) The velocity of diastolic (phase 4) depolarization (VDD) and rate of pacemaker firing (RPF) in normal pacemaker cells in SA nodes were decreased by NaHS (H(2)S donor) (50, 100, 200 µmol/L) in a concentration-dependent manner; (2) ATP-sensitive K(+) (K(ATP)) channel blocker glybenclamide (Gli, 20 µmol/L) blocked the effect of NaHS (100 µmol/L) on pacemaker cells; (3) Pretreatment with CsCl (2 mmol/L), a blocker of pacemaker current (I(f)), did not affect the effect of NaHS (100 µmol/L) on SA node pacemaker cells; (4) DL-propargylglycine (PPG, 200 µmol/L), an inhibitor of cystathionine γ-lyase (CSE), did not affect the parameters of action potentials in pacemaker cells in SA nodes. All these results suggest that H(2)S exerts a negative chronotropic action on pacemaker cells in SA nodes of rabbits. These effects are likely due to an increase in potassium efflux through opening K(ATP) channels; I(f)is unlikely to play a major role in these effects. In our study, there was no evidence for the generation of endogenous H(2)S by CSE in SA node pacemaker cells.