HCO (3)(-) secretion and CaCO3 precipitation play major roles in intestinal water absorption in marine teleost fish in vivo.
HCO (3)(-) secretion and CaCO3 precipitation play major roles in intestinal water absorption in marine teleost fish in vivo.
复制标题
HCO (3)(-) 分泌和 CaCO3 沉淀在海洋硬骨鱼体内肠道水分吸收中起主要作用。
DOI：
10.1152/ajpregu.00545.2009
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
R. Wilson
中科院分区：
文献类型：
--
作者：
J. Whittamore;C. Cooper;R. Wilson
The intestine of marine teleosts must effectively absorb fluid from ingested seawater to avoid dehydration. This fluid transport has been almost exclusively characterized as driven by NaCl absorption. However, an additional feature of the osmoregulatory role of the intestine is substantial net HCO(3)(-) secretion. This is suggested to drive additional fluid absorption directly (via Cl(-)/HCO(3)(-) exchange) and indirectly by precipitating ingested Ca(2+) as CaCO(3), thus creating the osmotic gradient for additional fluid absorption. The present study tested this hypothesis by perfusing the intestine of the European flounder in vivo with varying [Ca(2+)]: 10 (control), 40, and 90 mM. Fractional fluid absorption increased from 47% (control) to 73% (90 mM Ca(2+)), where almost all secreted HCO(3)(-) was excreted as CaCO(3). This additional fluid absorption could not be explained by NaCl cotransport. Instead, a significant positive relationship between Na(+)-independent fluid absorption and total HCO(3)(-) secretion was consistent with the predicted roles for anion exchange and CaCO(3) precipitation. Further analysis suggested that Na(+)-independent fluid absorption could be accounted for by net Cl(-) and H(+) absorption (from Cl(-)/HCO(3)(-) exchange and CO(2) hydration, respectively). There was no evidence to suggest that CaCO(3) alone was responsible for driving fluid absorption. However, by preventing the accumulation of luminal Ca(2+) it played a vital role by dynamically maintaining a favorable osmotic gradient all along the intestine, which permits substantially higher rates of solute-linked fluid absorption. To overcome the resulting hyperosmotic and highly acidic absorbate, it is proposed that plasma HCO(3)(-) buffers the absorbed H(+) (from HCO(3)(-) production), and consequently reduces the osmolarity of the absorbed fluid entering the body.
DOI：
10.1152/ajpregu.00513.2009
发表时间：
2010-04-01
影响因子：
2.8
作者：
Cooper, Christopher A.;Whittamore, Jonathan M.;Wilson, Rod W.
通讯作者：
Wilson, Rod W.