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|標題:||Short-term effects of hyposmotic shock on Na+/K+-ATPase expression in gills of the euryhaline milkfish, Chanos chanos||作者:||Lin, Y.M.
|關鍵字:||milkfish;Chanos chanos;euryhalinc teleost;gill;Na+/K+-ATPase;time-course;tilapia oreochromis-mossambicus;mitochondria-rich cells;killifish;fundulus-heteroclitus;trout salmo-trutta;fresh-water acclimation;time-course changes;k+-atpase;chloride cells;alpha-subunit;gene-expression||Project:||Comparative Biochemistry and Physiology a-Molecular & Integrative Physiology||期刊/報告no：:||Comparative Biochemistry and Physiology a-Molecular & Integrative Physiology, Volume 143, Issue 3, Page(s) 406-415.||摘要:||
Changes in expression of gill Na+/K+-ATPase (NKA) on a short-term (96 h) time-course following hyposmotic shock (direct transfer to fresh water) of the euryhaline, marine milkfish were studied on gene, protein, and cell levels in this paper. Plasma osmolality and [Na+] responded with rapid declines in 3 h post-transfer yet, thereafter, remained constant. Plasma [Cl-] gradually fell to a significantly lower level at 6 It post-transfer. Gills responded to hyposmotic shock by a dual phase enhancement of NKA activity and protein abundance; (a) Before 24 h: NKA activity increased as early as 3 h and reached a maximum level from 6 to 12 h post-transfer coincided with the sustained lower levels of plasma osmolality, [Na+], and [Cl-] since 3 h post-transfer. This was followed by a gradual rise in alpha-subunit protein levels that peaked at 12 It post-transfer. Meanwhile, a-mRNA of NKA did no show significant change. (b) After 24 h: NKA activity as well as the amounts of alpha-subunit mRNA and protein increased significantly. Direct freshwater transfer induced a prompt and significant decrease of NKA immunoreactive (NKIR) cell abundance in filaments before 24 h followed by a significant increase after 24 It due to their development in filaments and lamellae. Increased number of NKIR cells after 24 h of hyposmotic shock may occur in conjunction with rise of NKA activity as well as alpha-subunit mRNA and protein abundance. In conclusion, milkfish is able to avoid an excessive drop in plasma ions immediately upon hyposmotic shock and maintain plasma ions on a marginal lower level in fresh water. Notably, the initial increase in NKA activity (adjustive phase; 3-12 h) and delayed increase in NKA mRNA and protein abundance (regulatory phase; 48-96 h) indicate the importance of a higher level of the gill enzyme in milkfish upon hyposmotic shock. (c) 2005 Elsevier Inc. All rights reserved.
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