1. Hydrogen sulfide (H2S) and hypoxia inhibit salmonid gastrointestinal motility: evidence for H2S as an oxygen sensor.
- Author
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Dombkowski, Ryan A., Naylor, Marie G., Shoemaker, Emma, Smith, Michelle, DeLeon, Eric R., Stoy, Gilbrian F., Yan Gao, and Olson, Kenneth R.
- Subjects
HYDROGEN sulfide ,HYPOXEMIA ,GASTROINTESTINAL motility disorders ,METABOLISM ,RAINBOW trout ,COHO salmon - Abstract
Hydrogen sulfide (H
2 S) has been shown to affect gastrointestinal (GI) motility and signaling in mammals and O2 -dependent H2S metabolism has been proposed to serve as an O2 'sensor' that couples hypoxic stimuli to effector responses in a variety of other O2 -sensing tissues. The low PO2 values and high H2 S concentrations routinely encountered in the GI tract suggest that H2 S might also be involved in hypoxic responses in these tissues. In the present study we examined the effect of H2 S on stomach, esophagus, gallbladder and intestinal motility in the rainbow trout (Oncorhynchus mykiss) and coho salmon (Oncorhynchus kisutch) and we evaluated the potential for H2 S in oxygen sensing by examining GI responses to hypoxia in the presence of known inhibitors of H2 S biosynthesis and by adding the sulfide donor cysteine (Cys). We also measured H2 S production by intestinal tissue in real time and in the presence and absence of oxygen. In tissues exhibiting spontaneous contractions, H2 S inhibited contraction magnitude (area under the curve and amplitude) and frequency, and in all tissues it reduced baseline tension in a concentration-dependent relationship. Longitudinal intestinal smooth muscle was significantly more sensitive to H2 S than other tissues, exhibiting significant inhibitory responses at 1-10 μmol l-1 H2 S. The effects of hypoxia were essentially identical to those of H2 S in longitudinal and circular intestinal smooth muscle; of special note was a unique transient stimulatory effect upon application of both hypoxia and H2 S. Inhibitors of enzymes implicated in H2 S biosynthesis (cystathionine β-synthase and cystathionine γ-lyase) partially inhibited the effects of hypoxia whereas the hypoxic effects were augmented by the sulfide donor Cys. Furthermore, tissue production of H2 S was inversely related to O2 ; addition of Cys to intestinal tissue homogenate stimulated H2S production when the tissue was gassed with 100% nitrogen (~0% O2 ), whereas addition of oxygen (~10% O2 ) reversed this to net H2 S consumption. This study shows that the inhibitory effects of H2 S on the GI tract of a non-mammalian vertebrate are identical to those reported in mammals and they provide further evidence that H2 S is a key mediator of the hypoxic response in a variety of O2 -sensitive tissues. [ABSTRACT FROM AUTHOR]- Published
- 2011
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