1. Hydrogen sulfide as an oxygen sensor in trout gill chemoreceptors.
- Author
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Olson, Kenneth R., Healy, Michael J., Zhaohong Qin, Skovgaard, Nini, Vulesevic, Branka, Duff, Douglas W., Whitfield, Nathan L., Guangdong Yang, Rui Wang, and Perry, Steve F.
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HYDROGEN sulfide ,CHEMORECEPTORS ,SENSORY receptors ,VASCULAR smooth muscle ,GILLS - Abstract
O
2 chemoreceptors elicit cardiorespiratory reflexes in all vertebrates, but consensus on O2 -sensing signal transduction mechanism(s) is lacking. We recently proposed that hydrogen sulfide (H2 S) metabolism is involved in O2 sensing in vascular smooth muscle. Here, we examined the possibility that H2 S is an O2 sensor in trout chemoreceptors where the first pair of gills is a primary site of aquatic O2 sensing and the homolog of the mammalian carotid body. Intrabuccal injection of H2 S in unanesthetized trout produced a dose-dependent bradycardia and increased ventilatory frequency and amplitude similar to the hypoxic response. Removal of the first, but not second, pair of gills significantly inhibited H2 S-mediated bradycardia, consistent with the loss of aquatic chemoreceptors. mRNA for H2 S-synthesizing enzymes, cystathionine &x#03B2;-synthase and cystathionine-&x#03B3;-lyase, was present in branchial tissue. Homogenized gills produced H2 S enzymatically, and H2 S production was inhibited by O2 , whereas mitochondrial H2 S consumption was O2 dependent. Ambient hypoxia did not affect plasma H2 S in unanesthetized trout, but produced a Po2 -dependent increase in a sulfide moiety suggestive of increased H2 S production. In isolated zebrafish neuroepithelial cells, the putative chemoreceptive cells of fish, both hypoxia and H2 S, produced a similar ~10-mV depolarization. These studies are consistent with H2 S involvement in O2 sensing/signal transduction pathway(s) in chemoreceptive cells, as previously demonstrated in vascular smooth muscle. This novel mechanism, whereby H2 S concentration ([H2 S]) is governed by the balance between constitutive production and oxidation, tightly couples tissue [H2 S] to Po2 and may provide an exquisitely sensitive, yet simple, O2 sensor in a variety of tissues. [ABSTRACT FROM AUTHOR]- Published
- 2008
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