Vasoconstriction triggered by hydrogen sulfide: Evidence for Na+,K+,2Cl-cotransport and L-type Ca2+ channel-mediated pathway

Objectives This study examined the dose-dependent actions of hydrogen sulfide donor sodium hydrosulphide (NaHS) on isometric contractions and ion transport in rat aorta smooth muscle cells (SMC). Methods Isometric contraction was measured in ring aortas segments from male Wistar rats. Activity of Na+/K+-pump and Na+,K+,2Cl-cotransport was measured in cultured endothelial and smooth muscle cells from the rat aorta as ouabain-sensitive and ouabain-resistant, bumetanide-sensitive components of the 86Rb influx, respectively. Results NaHS exhibited the bimodal action on contractions triggered by modest depolarization ([K+]o=30 mM). At 10-4 M, NaHS augmented contractions of intact and endothelium-denuded strips by ~ 15% and 25%, respectively, whereas at concentration of 10-3 M it decreased contractile responses by more than two-fold. Contractions evoked by 10-4 M NaHS were completely abolished by bumetanide, a potent inhibitor of Na+,K+,2Cl-cotransport, whereas the inhibition seen at 10-3 M NaHS was suppressed in the presence of K+ channel blocker TEA. In cultured SMC, 5×10-5 M NaHS increased Na+,K+,2Cl- - cotransport without any effect on the activity of this carrier in endothelial cells. In depolarized SMC, 45Ca influx was enhanced in the presence of 10-4 M NaHS and suppressed under elevation of [NaHS] up to 10-3 M. 45Ca influx triggered by 10-4 M NaHS was abolished by bumetanide and L-type Ca2+ channel blocker nicardipine. Conclusions Our results strongly suggest that contractions of rat aortic rings triggered by low doses of NaHS are mediated by activation of Na+,K+,2Cl-cotransport and Ca2+ influx via L-type channels.