Intestinal bicarbonate secretion by marine teleost fish--why and how?
Intestinal bicarbonate secretion by marine teleost fish--why and how?
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海洋硬骨鱼肠道分泌碳酸氢盐——为什么以及如何分泌？
DOI：
10.1016/s0005-2736(02)00600-4
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
M. Grosell
中科院分区：
文献类型：
--
作者：
R. Wilson;Jonathan M. Wilson;M. Grosell
大多数海洋硬骨鱼的肠液呈碱性（pH 8.4-9.0），含有高水平的HCO3 -当量（40-130 mM），排泄速度显著（bbb100 μEq kg−1h−1）。最近的研究揭示了HCO3−的大量分泌：(1)HCO3−不参与酸碱调节或胃酸的中和，但在环境盐度升高时，它与饮用率平行增加，提示在渗透调节中起作用；(2)在目前所研究的物种中，肠道的所有部分都能分泌碳酸氢盐；(3)分泌依赖于粘膜Cl -，对粘膜DIDS敏感，免疫组织化学表明参与根尖Cl - /HCO3 -交换器。此外，二氧化碳通过碳酸酐酶的水合作用和质子挤压作用似乎对碳酸氢盐的分泌至关重要。质子挤压的方式目前尚不清楚，但讨论了可能的机制。腔内碱度和高碳酸氢盐浓度的一个后果是钙和镁作为碳酸盐络合物的沉淀。据推测，这种沉淀可以降低肠道液体的渗透压，从而在水分吸收和渗透调节中发挥潜在作用。目前对欧洲比目鱼的研究表明，在体外和体内，升高的腔内钙（而不是镁）浓度会急性和慢性地刺激肠道碳酸氢盐分泌。在全动物水平上，碳酸氢盐分泌增加的结果是钙沉淀增加，同时直肠液体和血浆渗透压降低。这些观察结果表明，海洋硬骨鱼肠道碳酸氢盐分泌、二价阳离子沉淀和渗透调节之间存在直接的功能联系。
Intestinal fluids of most marine teleosts are alkaline (pH 8.4–9.0) and contain high levels of HCO3−equivalents (40–130 mM) which are excreted at a significant rate (>100 μEq kg−1h−1). Recent research reveals the following about this substantial HCO3−secretion: (1) It is not involved in acid–base regulation or neutralisation of stomach acid, but increases in parallel with drinking rate at elevated ambient salinities suggesting a role in osmoregulation; (2) In species examined so far, all sections of the intestine can secrete bicarbonate; (3) The secretion is dependent on mucosal Cl−, sensitive to mucosal DIDS, and immuno-histochemistry indicates involvement of an apical Cl−/HCO3−exchanger. In addition, hydration of CO2via carbonic anhydrase in combination with proton extrusion appears to be essential for bicarbonate secretion. The mode of proton extrusion is currently unknown but potential mechanisms are discussed. One consequence of the luminal alkalinity and high bicarbonate concentrations is precipitation of calcium and magnesium as carbonate complexes. This precipitation is hypothesised to reduce the osmolality of intestinal fluids and thus play a potential role in water absorption and osmoregulation. The present studies on European flounder reveal that elevated luminal calcium (but not magnesium) concentrations stimulate intestinal bicarbonate secretion both acutely and chronically, in vitro and in vivo. At the whole animal level, the result of this elevated bicarbonate secretion was increased calcium precipitation with an associated reduction in the osmolality of rectal fluids and plasma. These observations suggest direct functional links between intestinal bicarbonate secretion, divalent cation precipitation and osmoregulation in marine teleost fish.
DOI：
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发表时间：
1996
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
M. Ruat;A. Snowman;L. D. Hester;S. H. Snyder
通讯作者：
M. Ruat;A. Snowman;L. D. Hester;S. H. Snyder
DOI：
10.1152/ajpcell.1997.273.4.c1168
发表时间：
1997-10-01
影响因子：
5.5
作者：
Gama, L;BaxendaleCox, LM;Breitwieser, GE
通讯作者：
Breitwieser, GE
大鼠近曲小管的反射系数和水渗透性。
DOI：
10.1152/ajprenal.1989.257.4.f658
发表时间：
1989
期刊：
The American journal of physiology
影响因子：
--
作者：
Green,R;Giebisch,G
通讯作者：
Giebisch,G