The effect of environmental hypercapnia and salinity on the expression of NHE-like isoforms in the gills of a euryhaline fish (Fundulus heteroclitus)

Edwards, Susan L., Wall, Brian P., Morrison-Shetlar, Alison, Sligh, Samuel, Weakly, Jill C., and Claiborne, James B. (2005) The effect of environmental hypercapnia and salinity on the expression of NHE-like isoforms in the gills of a euryhaline fish (Fundulus heteroclitus). Journal of Experimental Zoology, Part A, 303A (6). pp. 464-475.

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Abstract

The current models for branchial acid excretion in fishes include Na+/H+ exchange and the electrogenic excretion of H+ via H+-ATPase. The predominant route of acid excretion in some freshwater fishes is thought to be via the H+-ATPase/Na+ channel system. The euryhaline Fundulus heteroclitus may not fit this profile even when adapted to freshwater (FW). We hypothesize that the Na+/H+ exchanger (NHE) in this species may play a predominant role in acid-base regulation for both marine and FW adapted animals. Acidosis induced by ambient hypercapnia (1% CO2 in air), resulted in an increase in net H+ excretion to the water in F. heteroclitus pre-adapted to FW, brackish (isoosmotic; BW) and seawater (SW). Both FW and SW adapted mummichogs were tested for NHE protein expression using mammalian NHE antibodies, and we identified NHE-like immunoreactive proteins in gill membrane preparations from both groups. Hypercapnia induced a ∼three-fold elevation in gill NHE2-like protein in FW animals but SW adapted fish showed inconsistent NHE3-like protein expression. There was no change in NHE-1 levels in FW fish. In contrast, SW animals demonstrated a significant increase in both NHE1 and NHE3-like proteins following hypercapnia but limited expression of the NHE2 protein. We hypothesize that different isoforms of NHE may be preferentially expressed depending on the salinity to which the animals are adapted. Net H+ transfers during acidosis may be driven, at least in part by the action of these transporters.

Item ID: 14038
Item Type: Article (Research - C1)
ISSN: 1932-5231
Date Deposited: 25 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 > 060603 Animal Physiology Systems @ 33%
06 BIOLOGICAL SCIENCES > 0606 Physiology > 060604 Comparative Physiology @ 33%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960802 Coastal and Estuarine Flora, Fauna and Biodiversity @ 34%
97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 33%
93 EDUCATION AND TRAINING > 9399 Other Education and Training > 939999 Education and Training not elsewhere classified @ 33%
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