OBJECTIVETo review the vasorelaxant effects of hydrogen sulfide (H(2)S) in arterial rings in the cardiovascular system under both physiological and pathophysiological conditions and the possible mechanisms involved.

DATA SOURCESThe data in this review were obtained from Medline and Pubmed sources from 1997 to 2011 using the search terms "hydrogen sulfide" and "vascular relaxation".

STUDY SELECTIONArticles describing the role of hydrogen sulfide in the regulation of vascular activity and its vasorelaxant effects were selected.

RESULTSH(2)S plays an important role in the regulation of cardiovascular tone. The vasomodulatory effects of H(2)S depend on factors including concentration, species and tissue type. The H(2)S donor, sodium hydrosulfide (NaHS), causes vasorelaxation of rat isolated aortic rings in a dose-dependent manner. This effect was more pronounced than that observed in pulmonary arterial rings. The expression of K(ATP) channel proteins and mRNA in the aortic rings was increased compared with pulmonary artery rings. H(2)S is involved in the pathogenesis of a variety of cardiovascular diseases. Downregulation of the endogenous H(2)S pathway is an important factor in the pathogenesis of cardiovascular diseases. The vasorelaxant effects of H(2)S have been shown to be mediated by activation of K(ATP) channels in vascular smooth muscle cells and via the induction of acidification due to activation of the Cl(-)/HCO(3)(-) exchanger. It is speculated that the mechanisms underlying the vasoconstrictive function of H(2)S in the aortic rings involves decreased NO production and inhibition of cAMP accumulation.

CONCLUSIONH(2)S is an important endogenous gasotransmitter in the cardiovascular system and acts as a modulator of vascular tone in the homeostatic regulation of blood pressure.