|ZFIN ID: ZDB-PUB-100112-18|
Zebrafish (Danio rerio) gill neuroepithelial cells are sensitive chemoreceptors for environmental CO2
Qin, Z., Lewis, J.E., and Perry, S.F.
|Source:||The Journal of physiology 588(Pt 5): 861-872 (Journal)|
|Registered Authors:||Perry, Steve F.|
|Keywords:||carbon dioxide, Carbonic anhydrase, Chemoreceptor|
|PubMed:||20051495 Full text @ J. Physiol.|
Qin, Z., Lewis, J.E., and Perry, S.F. (2010) Zebrafish (Danio rerio) gill neuroepithelial cells are sensitive chemoreceptors for environmental CO2. The Journal of physiology. 588(Pt 5):861-872.
ABSTRACTAdult zebrafish exhibit hyperventilatory responses to absolute environmental CO2 levels as low as 0.13% (PCO2 = 1.0 mm Hg), more than an order of magnitude lower than the typical arterial PCO2 levels (~40 mm Hg) monitored by the mammalian carotid body. The sensory basis underlying the ability of fish to detect and respond to low ambient CO2 levels is not clear. Here, we show that the neuroepithelial cells (NECs) of the zebrafish gill, known to sense O2 levels, also respond to low levels of CO2. An electrophysiological characterization of this response using both current and voltage clamp protocols revealed that for increasing CO2 levels, a background K+ channel was inhibited, resulting in a partial pressure-dependent depolarization of the NEC. To elucidate the signaling pathway underlying K+ channel inhibition, we used immunocytochemistry to show that these NECs express carbonic anhydrase (CA), an enzyme involved in CO2 sensing in the mammalian carotid body. Further, the NEC response to CO2 (magnitude of membrane depolarization and time required to achieve maximal response), under conditions of constant pH, was reduced by ~50% by the CA-inhibitor acetazolamide. This suggests that the CO2 detection mechanism involves an intracellular sensor that is responsive to the rate of acidification associated with the hydration of CO2 and which does not require a change of extracellular pH. Because some cells that were responsive to increasing PCO2 also responded to hypoxia with membrane depolarization, the present results demonstrate that a subset of the NECs in the zebrafish gill are bimodal sensors of CO2 and O2.
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