| Summary: | 碩士 === 國立臺灣大學 === 漁業科學研究所 === 89 === The purpose of the present study is to examine the expression and activation of Na+- K+-ATPase α isoforms in tilapia (Oreochromis mossambicus) during seawater (SW) adaptation. Plasma osmolarity and enzyme activity and protein expression of Na+- K+-ATPase in gills and brain were measured in tilapia transferred from freshwater (FW) to 25 ‰ SW. The results showed that plasma osmolarity increased 3 hr after transfer, then started to decrease at 48 hr, and recovered to the same level as the FW control at 168 hr after transfer. Na+- K+-ATPase activities increased about 1.7 folds in gills and 6.5 folds in brain during the first 6 hr. The remarkable activation of Na pump in tilapia brain during SW adaptation indicates that the central nervous system may be extremely sensitive to plasma osmolarity disturbance. In the western blot experimemt, both of the two isoforms, α1 and α3, were expressed in tilapia gills, but only α3 isoform could be detected in brain tissue of tilapia. The expression of the two isoforms was enhanced in both gills and brain during SW adaptation. However, activities of Na pump in both gills and brain were up-regulated before protein changes in the tissues, indicating that post-translational regulations of Na+- K+-ATPase may be involved in the short-term regulation of Na pump activity.
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