The gill, with a large surface area in intimate contact with the environment, is the primary organ of ion and acid-base regulation in fish. These same characteristics make the gill epithelium particularly susceptible to a number of environmental perturbations, including osmotic challenges and metabolic acidosis. For most freshwater fish, the active uptake of the strong ions, sodium and chloride, are intimately linked with the excretion of acid and base equivalents, respectively. However, fish from the genus Fundulus, are unique in their apparent lack of active chloride uptake at the gills. This unique feature makes limiting Cl- loss through paracellular pathways the only practical strategy for these species in tolerating acute exposure to hypoosmotic conditions especially when dietary chloride is limited. We find that Fundulus grandis can dynamically regulate their paracellular pathway in the gill epithelium at salinities approaching fresh water. We observe the significant up-regulation in the mRNA levels of several claudins in the gill and that some of these claudinsexhibit expressional discrepancies between mitochondrion-rich and pavement cells in fish gills, which shows correlations with changes in gill morphology and ion flux rates in fish. Collectively, our data suggest that claudins may play important roles in regulating ion flux across paracellular pathways of Fundulus during osmotic challenges.
The linkage between osmoregulation and acid-base tolerance has long been studied in teleost fish. Failure to identify an active Cl- uptake system in freshwater Fundulusindicates the uniqueness of these species in osmoregulation and acid-base tolerance. We find that Fundulus heteroclitus increases Na+ uptake within the first few hours of metabolic acidosis,We also find that metabolic acidosis induces the changes of mRNA levels of several gill claudin proteins, which may play roles in regulating the permeability of the paracellular pathway to strong ions. Our data show Fundulus heteroclitus is capable to cope with great metabolic acidosis within their bodies, which may contribute to their adaptation to internal and external perturbations.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-07042012-093921 |
| Date | 11 July 2012 |
| Creators | Zhang, Shujun |
| Contributors | Andrew Whitehead, Gentry T. Glen, Evanna L Gleason, Steven C Hand, Fernando Galvez |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-07042012-093921/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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