Ca2+-driven intestinal HCO3- secretion and CaCO3 precipitation in the European flounder in vivo: influences on acid-base regulation and blood gas transport
Ca2+-driven intestinal HCO3- secretion and CaCO3 precipitation in the European flounder in vivo: influences on acid-base regulation and blood gas transport
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DOI：
10.1152/ajpregu.00513.2009
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发表时间：
2010-04-01
影响因子：
2.8
通讯作者：
Wilson, Rod W.
中科院分区：
文献类型：
--
作者：
Cooper, Christopher A.;Whittamore, Jonathan M.;Wilson, Rod W.
Cooper CA, Whittamore JM, Wilson RW. Ca2+-driven intestinal HCO3- secretion and CaCO3 precipitation in the European flounder in vivo: influences on acid-base regulation and blood gas transport. Am J Physiol Regul Integr Comp Physiol 298: R870-R876, 2010. First published February 3, 2010; doi: 10.1152/ajpregu.00513.2009.-Marine teleost fish continuously ingest seawater to prevent dehydration and their intestines absorb fluid by mechanisms linked to three separate driving forces: 1) cotransport of NaCl from the gut fluid; 2) bicarbonate (HCO3-) secretion and Cl- absorption via Cl-/HCO3- exchange fueled by metabolic CO2; and 3) alkaline precipitation of Ca2+ as insoluble CaCO3, which aids H2O absorption). The latter two processes involve high rates of epithelial HCO3- secretion stimulated by intestinal Ca2+ and can drive a major portion of water absorption. At higher salinities and ambient Ca2+ concentrations the osmoregulatory role of intestinal HCO3- secretion is amplified, but this has repercussions for other physiological processes, in particular, respiratory gas transport (as it is fueled by metabolic CO2) and acid-base regulation (as intestinal cells must export H+ into the blood to balance apical HCO3- secretion). The flounder intestine was perfused in vivo with salines containing 10, 40, or 90 mM Ca-2(+). Increasing the luminal Ca2+ concentration caused a large elevation in intestinal HCO3- production and excretion. Additionally, blood pH decreased (similar to 0.13 pH units) and plasma partial pressure of CO2 (PCO2) levels were elevated (+1.16 mmHg) at the highest Ca perfusate level after 3 days of perfusion. Increasing the perfusate [Ca2+] also produced proportional increases in net acid excretion via the gills. When the net intestinal flux of all ions across the intestine was calculated, there was a greater absorption of anions than cations. This missing cation flux was assumed to be protons, which vary with an almost 1:1 relationship with net acid excretion via the gill. This study illustrates the intimate link between intestinal HCO3- production and osmoregulation with acid-base balance and respiratory gas exchange and the specific controlling role of ingested Ca2+ independent of any other ion or overall osmolality in marine teleost fish.
