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標題: 比較來自不同棲息地的廣鹽性硬骨魚類吳郭魚和虱目魚在不同鹽度環境中腎臟Na+/K+-ATPaseα-subunit isoforms的變化
Comparisons of switches of Na+/K+-ATPase α-isoform proteins between kidneys of two euryhaline teleots, tilapia (Oreochromis mossambicus) and milkfish (Chanos chanos), from different primary natural habitats in response to salinity challenge
作者: 鍾昌宏
Chung, Chang-Hung
關鍵字: tilapia
出版社: 生命科學院碩士在職專班
摘要: 莫三比克吳郭魚(Oreochromis mossambicus)是一種生活於淡水的硬骨魚類,其原棲地為非洲南部的淡水水域。虱目魚(Chanos chanos)是一種海洋的硬骨魚類,廣泛分部於熱帶至亞熱帶的印度洋及太平洋。吳郭魚及虱目魚皆屬於廣鹽性硬骨魚類,無論在高張的海水環境或低張的淡水環境下皆可生存。當面臨不同鹽度環境的挑戰時,鰓上Na+/K+-ATPase (NKA)活性會不同,且NKA對鈉離子與鉀離子的親和力亦發生改變,推測可能與不同NKA α-subunit isoforms表現有關。除了以鰓進行離子調節,腎臟亦為硬骨魚滲透壓調節的重要器官。然而,過去對於腎臟離子調節機轉的研究較少,因此,為了比較來自不同棲息地的廣鹽性硬骨魚類吳郭魚和虱目魚腎臟的離子調節機轉,本實驗主要在探討腎臟在不同鹽度環境中Na+/K+-ATPase α-subunit isoforms的變化。將莫三比克吳郭魚及虱目魚長期馴養於淡水(0‰)和海水(35‰)二種不同的鹽度環境二週以上,並且利用免疫轉漬法進行蛋白質含量的比較。結果顯示,長期馴養在海水的莫三比克吳郭魚,其腎臟NKA α-subunit、α1-與α3-isoform蛋白質含量顯著高於長期馴養於淡水的莫三比克吳郭魚,相反地,NKA α2-isoform的蛋白質表現量為淡水較海水高。至於長期馴養在淡水的虱目魚,其腎臟NKA α-subunit與α1-isoform蛋白質含量顯著高於長期馴養於海水的虱目魚,但α2-與α3-isoform蛋白質含量則無顯著差異。綜合上述結果顯示:(1)莫三比克吳郭魚及虱目魚NKA在腎臟的表現受環境鹽度的影響,當面臨與原棲地不同鹽度的挑戰時,NKA α-subunit有顯著上升的現象,且α-isoforms的蛋白質表現量亦會受環境鹽度影響而改變;(2)不論是淡水轉移到海水的莫三比克吳郭魚,或是海水轉移到淡水的虱目魚,其NKA α1-isoform的蛋白質表現量皆顯著上升,故推測α1-isoform可能為腎臟中負責滲透壓調節功能最主要的α-isoform,有助於廣鹽性硬骨魚面對不同鹽度挑戰而進行離子調節的生理機轉。
Mozambique tilapia (Oreochromis mossambicus) is a kind of freshwater teleost whose natural habitats are in fresh water of southern Africa. Milkfish (Chanos chanos) is a kind of marine teleost widely distributed throughout the tropical and subtropical Indo-Pacific. Both Mozambique tilapia and milkfish are euryhaline teleosts and can survive in a broad range of salinity. Since the activity and Na+ and K+ affinities of branchial Na+/K+-ATPase (NKA) changed with environmental salinities, it is suggested that the difference may be due to the switches of NKA α-subunit isoforms. The kidney is another important organ responsible for ion-regulation in teleosts. However, few studies addressed on the mechanisms of ion-regulation in kidney. In order to compare the ion-regulation mechanism between two euryhaline teleosts from different primary natural habitats in response to salinity challenge, this study focus on the switches of renal NKA α-isoform proteins between tilapia (Oreochromis mossambicus) and milkfish (Chanos chanos). Mozambique tilapia and milkfish were acclimatized and reared in seawater (35‰) and fresh water, respectively, for more than two weeks before sampling. In Mozambique tilapia, the protein abundance of renal NKA α-subunit, α1-, and α3-isoform in seawater-acclimatized fish was significantly higher than in freshwater acclimatized group. On the other hand, the α2-isoform was significantly lower in freshwater acclimatized individuals. In freshwater acclimatized milkfish, the protein abundance of renal NKA α-subunit and α1-isoform was significantly higher than in seawater-acclimatized group. As for α2- and α3-isoform, the protein abundance reveals no significant difference between different salinity groups. In conclusion, the protein abundance of renal NKA α-subunit was significantly higher in SW-acclimatized Mozambique tilapia and FW-acclimatized milkfish, and the protein abundance of renal NKA α-isoforms was influenced by environmental different salinities. In addition, the switches of renal NKA α-isoforms, especially α1-isoform, may be involved in the mechanisms of ion regulation in FW- and SW-acclimatized Mozambique tilapia and milkfish.
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