Intrarenal oxygenation: Unique challenges and the biophysical basis of homeostasis

Roger George Evans, Bruce S Gardiner, David Wamsley Smith, P M O'Connor

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176 Citations (Scopus)

Abstract

The kidney is faced with unique challenges for oxygen regulation, both because its function requires that perfusion greatly exceeds that required to meet metabolic demand and because vascular control in the kidney is dominated by mechanisms that regulate glomerular filtration and tubular reabsorption. Because tubular sodium reabsorption accounts for most oxygen consumption (VO2) in the kidney, renal VO2 varies with glomerular filtration rate. This provides an intrinsic mechanism to match changes in oxygen delivery due to changes in renal blood flow (RBF) with changes in oxygen demand. Renal VO2 is low relative to supply of oxygen, but diffusional arterial-to-venous (AV) oxygen shunting provides a mechanism by which oxygen superfluous to metabolic demand can by-pass the renal microcirculation. This mechanism prevents development of tissue hyperoxia and subsequent tissue oxidation that would otherwise result from the mis-match between renal VO2 and RBF. Recent evidence suggests that RBF-dependent changes in AV oxygen shunting may also help maintain stable tissue oxygen tension when RBF changes within the physiological range. But AV oxygen shunting also renders the kidney susceptible to hypoxia. Given tissue hypoxia is a hallmark of both acute renal injury and chronic renal disease, understanding the causes of tissue hypoxia is of great clinical importance. The simplistic paradigm of oxygenation depending only on the balance between local perfusion and VO2 is inadequate to achieve this goal. To fully understand the control of renal oxygenation we must consider a triad of factors that regulate intrarenal oxygenation; local perfusion, local VO2 and AV oxygen shunting. Key words: counter-current exchange, diffusional oxygen shunting, hypoxia, kidney circulation.
Original languageEnglish
Pages (from-to)F1259 - F1270
Number of pages12
JournalAmerican Journal of Physiology-Renal Physiology
Volume295
Issue number5
Publication statusPublished - 2008

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