Intestinal osmoregulatory acclimation and nitrogen

Authors: Shit F Chew Yvonne Y M Tng Nicklaus L J Wee Chia Y Tok Jonathan M Wilson Yuen K Ip

Publish Date: 2009/12/19

Volume: 180, Issue: 4, Pages: 511-520

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Abstract

The objective of this study was to elucidate the role of the intestine from juveniles of the marble goby Oxyeleotris marmorata during seawater SW exposure It has been reported elsewhere that SWexposed juvenile O marmorata exhibits hypoosmotic and hypoionic regulation with the induction of branchial Na+/K+ATPase NKA Na+K+2Cl− cotransporter NKCC and cystic fibrosis transmembrane receptorlike chloride channels Here we report that SW exposure also led to significant increases in the activity and protein abundance of NKA in and probably an increase in Na+ uptake through its intestine Additionally there was an increase in apical NKCC immunoreactivity in the intestinal epithelium indicating that there could be increased Cl− uptake through the intestine These results suggest that absorption of ions and hence water from the intestinal lumen could be an essential part of the osmoregulatory process in juvenile O marmorata during exposure to SW Furthermore there were significant increases in the glutamate content and the aminating activity and protein abundance of glutamate dehydrogenase GDH in the intestine of fish exposed to SW Since the intestinal glutamine synthetase activity and protein abundance decreased significantly and the intestinal glutamine content remained unchanged in the SWexposed fish excess glutamate formed via increased GDH activity in the intestine could be channeled to other organs to facilitate the increased synthesis of amino acids Taken together our results indicate for the first time that besides absorbing ions and water during SW exposure the intestine of juvenile O marmorata also participated in altered nitrogen metabolism in response to salinity changes

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