What is the significance of vascular hydrogen sulphide (H 2 S)?

The important role of nitric oxide (NO) in the regulation of vascular tone has been well studied. By contrast, the vascular significance of another gaseous mediator, hydrogen sulphide (H 2 S), is still poorly understood. A study published in this issue of the British Journal of Pharmacology now provides evidence that in addition to the vasorelaxant effects of H 2 S reported in vitro , low concentrations of H 2 S also cause arterial vasoconstriction, reverse NO‐mediated vasorelaxation and cause an NO‐dependent pressor effect in vivo . This commentary discusses the implications and questions raised by these results. British Journal of Pharmacology (2006) 149 , 609–610. doi: 10.1038/sj.bjp.0706907