H2S modulates cardiac function of the frog

Recently, a third endogenous gaseous signaling molecule, hydrogen sulfide (H2S), has emerged as an important mediator of cardiovascular homeostasis, with biochemical properties similar to carbon monoxide and nitric oxide. The role of H2S in the mammalian cardiovascular system is well documented. In rat, H2S induces a dose-dependent relaxation of arteries and veins in vitro, a reduction of blood pressure in vivo and a negative inotropism in perfused hearts (Geng et al., 2004, Biochem. Biophys. Res. Commun. 313: 362–368).In non mammalian vertebrates, vasoactive properties of H2S have been also demonstrated in at least one species from each class of vertebrates (Dombkowski et al., 2005, Am. J. Physiol. 288: R243–R252). In contrast, nothing is known about the cardiac effects of H2S in non mammalian vertebrates.The purpose of the present study was to assess the effects of H2S on the avascular heart of the frog Rana esculenta. Perfusion of isolated heart with a donor of H2S, sodium hydrosulfide (NaHS; 10­11–10­7M) significantly reduced the stroke volume (used as index of inotropism) in a concentration-dependent manner. This effect involved KATP channels while appeared independent from NOS-cGMP pathway.Our preliminary data support the hypothesis that H2S may represent a phylogenetically ancient cardioactive molecule. Studies are in progress to examine the mechanism of action involved in the cardiac action of H2S.