Gene expression after freshwater transfer in gills and opercular epithelia of killifish: insight into divergent mechanisms of ion transport

Scott, Graham R., Claiborne, James B., Edwards, Susan L., Schulte, Patricia M., and Wood, Chris M. (2005) Gene expression after freshwater transfer in gills and opercular epithelia of killifish: insight into divergent mechanisms of ion transport. Journal of Experimental Biology, 208 (14). pp. 2719-2729.

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We have explored the molecular basis for differences in physiological function between the gills and opercular epithelium of the euryhaline killifish Fundulus heteroclitus. These tissues are functionally similar in seawater, but in freshwater the gills actively absorb Na+ but not Cl–, whereas the opercular epithelium actively absorbs Cl– but not Na+. These differences in freshwater physiology are likely due to differences in absolute levels of gene expression (measured using real-time PCR), as several proteins important for Na+ transport, namely Na+,H+-exchanger 2 (NHE2), carbonic anhydrase 2 (CA2), Na+,HCO3–cotransporter 1, and V-type H+-ATPase, were expressed at 3- to over 30-fold higher absolute levels in the gills. In gills, transfer from 10% seawater to freshwater increased the activity of Na+,K+-ATPase by twofold (from 12 h to 7 days), increased the expression of NHE2 (at 12 h) and CA2 (from 12 h to 7 days), and decreased the expression of NHE3 (from 12 h to 3 days). In opercular epithelium, NHE2 was not expressed; furthermore, Na+,K+-ATPase activity was unchanged after transfer to freshwater, CA2 mRNA levels decreased, and NHE3 levels increased. Consistent with their functional similarities in seawater, killifish gills and opercular epithelium expressed Na+,K+-ATPase {alpha}1a, Na+,K+,2Cl–cotransporter 1 (NKCC1), cystic fibrosis transmembrane conductance regulator (CFTR) Cl– channel and the signalling protein 14-3-3a at similar absolute levels. Furthermore, NKCC1 and CFTR were suppressed equally in each tissue after freshwater transfer, and 14-3-3a mRNA increased in both. These results provide insight into the mechanisms of ion transport by killifish gills and opercular epithelia, and demonstrate a potential molecular basis for the differences in physiological function between these two organs.

Item ID: 14037
Item Type: Article (Research - C1)
ISSN: 1477-9145
Keywords: Fundulus heteroclitus, carbonic anhydrase, Na+, H+-exchanger, Na+, HCO3–cotransporter, fish
Date Deposited: 26 Nov 2010 05:16
FoR Codes: 07 AGRICULTURAL AND VETERINARY SCIENCES > 0707 Veterinary Sciences > 070702 Veterinary Anatomy and Physiology @ 34%
06 BIOLOGICAL SCIENCES > 0606 Physiology > 060604 Comparative Physiology @ 33%
06 BIOLOGICAL SCIENCES > 0606 Physiology > 060603 Animal Physiology Systems @ 33%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960802 Coastal and Estuarine Flora, Fauna and Biodiversity @ 34%
93 EDUCATION AND TRAINING > 9399 Other Education and Training > 939999 Education and Training not elsewhere classified @ 33%
97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 33%
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