Effects of pH and medullary blood flow on oxygen transport and sodium reabsorption in the rat outer medulla

被引:35
作者
Chen, Jing [2 ]
Edwards, Aurelie [1 ]
Layton, Anita T. [2 ]
机构
[1] Tufts Univ, Dept Biol & Chem Engn, Medford, MA 02155 USA
[2] Duke Univ, Dept Math, Durham, NC 27706 USA
基金
美国国家科学基金会; 美国国家卫生研究院;
关键词
mathematical model; thick ascending limb; T-Na/QO(2) ratio; paracellular; transcellular; THICK ASCENDING LIMB; URINE CONCENTRATING MECHANISM; MATHEMATICAL-MODEL; VASA-RECTA; COLLECTING DUCTS; ANGIOTENSIN-II; PROTEIN-INTAKE; O-2; TRANSPORT; KIDNEY; ARCHITECTURE;
D O I
10.1152/ajprenal.00572.2009
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
Chen J, Edwards A, Layton AT. Effects of pH and medullary blood flow on oxygen transport and sodium reabsorption in the rat outer medulla. Am J Physiol Renal Physiol 298: F1369-F1383, 2010. First published March 24, 2010; doi: 10.1152/ajprenal.00572.2009.-We used a mathematical model of O-2 transport and the urine concentrating mechanism of the outer medulla of the rat kidney to study the effects of blood pH and medullary blood flow on O-2 availability and Na+ reabsorption. The model predicts that in vivo paracellular Na+ fluxes across medullary thick ascending limbs (mTALs) are small relative to transcellular Na+ fluxes and that paracellular fluxes favor Na+ reabsorption from the lumen along most of the mTAL segments. In addition, model results suggest that blood pH has a significant impact on O-2 transport and Na+ reabsorption owing to the Bohr effect, according to which a lower pH reduces the binding affinity of hemoglobin for O-2. Thus our model predicts that the presumed greater acidity of blood in the interbundle regions, where mTALs are located, relative to that in the vascular bundles, facilitates the delivery of O-2 to support the high metabolic requirements of the mTALs and raises the concentrating capability of the outer medulla. Model results also suggest that increases in vascular and tubular flow rates result in disproportional, smaller increases in active O-2 consumption and mTAL active Na+ transport, despite the higher delivery of O-2 and Na+. That is, at a sufficiently high medullary O-2 supply, O-2 demand in the outer medulla does not adjust precisely to changes in O-2 delivery.
引用
收藏
页码:F1369 / F1383
页数:15
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