Effects of hydrogen sulphide on the isolated perfused rat heart

Objectives: Hydrogen sulphide has been identified as a gas signalling molecule in the body, and has previously been shown to have vasorelaxant properties. The aim of the study was to investigate the effects of sodium hydrosulphide (NaHS), a hydrogen sulphide donor, on heart rate (HR), left ventricular developed pressure (LVDP) and coronary flow (CF) in the isolated perfused rat heart. Methods: A Langendorff isolated heart preparation was used to investigate the effect of a dose range of sodium hydrosulphide, in the presence and absence of inhibitors, on heart rate, left ventricular developed pressure and coronary flow. Results: Sodium hydrosulphide caused a significant decrease in heart rate at a concentration of 10-3 M (P <0.001). This decrease was partially inhibited by glibenclamide, a K ATP channel blocker (P <0.05); L-NAME, a nitric oxide synthase inhibitor (P <0.001), and methylene blue (P <0.001), but not by H-89, a protein kinase A inhibitor. Sodium hydrosulphide significantly increased coronary flow at concentrations of 10-4 - 10-3M (P <0.05). This response was significantly increased in the presence of L-NAME (P <0.001) and methylene blue (P <0.001), whereas H-89 inhibited the increase in coronary flow due to sodium hydrosulphide (P <0.001). Sodium hydrosulphide significantly decreased LVDP at all concentrations (P <0.001). In the presence of glibenclamide and H-89, the time period of the decrease in LVDP due to sodium hydrosulphide was extended (P <0.001), whereas methylene blue and L-NAME caused a significant reduction in the response to sodium hydrosulphide (P <0.05, P <0.01 respectively). Conclusion: Sodium hydrosulphide reduced heart rate and LVDP, and increased coronary flow in the isolated perfused rat heart; however, the mechanisms of action could not be fully elucidated.

(Table 2) Hydrogen sulphide and methane content, and loss on ignition in sediments obtained in the Gotland Deep, Baltic Sea

The distribution of methane and hydrogen sulfide concentrations in sediments of various basins of the Baltic Sea was investigated during 4 cruises in 1995 and 1996. Significant differences in the concentrations of both compounds were recorded between the basins and also between different areas within the Gotland Deep. High-methane sediments with distinctly increasing concentrations from the surface to deeper layers were distinguished from low-methane sediments without a clear gradient. Methane concentrations exhibited a fair correlation with the sediment accumulation rate, determined by measuring the total thickness of the post-Ancylus Holocene sequence on echosounding profiles in the Gotland Deep. Only weak correlations were observed with the content of organic matter in the surface layers of the sediments. Hydrogen sulfide concentrations in the sediments showed a positive correlation with methane concentrations, but, in contrast to methane concentrations, were strongly influenced by the transition from oxic to anoxic conditions in the water column between 1995 and 1996. Sediments in the deepest part of the Gotland Basin (>237 m water depth), covering an area of approximately 35 km**2, were characterized by especially high accumulation rates (>70 cm/ka) and high methane and hydrogen sulfide contents. Concentrations of these compounds decreased rapidly towards the slope of the basin.