Root effect hemoglobin may have evolved to enhance general tissue oxygen delivery

Rummer, Jodie L., McKenzie, David J., Innocenti, Alessio, Supuran, Claudiu T., and Brauner, Colin J. (2013) Root effect hemoglobin may have evolved to enhance general tissue oxygen delivery. Science, 340 (6138). pp. 1327-1329.

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The Root effect is a pH-dependent reduction in hemoglobin-O2 carrying capacity. Specific to ray-finned fishes, the Root effect has been ascribed specialized roles in retinal oxygenation and swimbladder inflation. We report that when rainbow trout are exposed to elevated water carbon dioxide (CO2), red muscle partial pressure of oxygen (PO2) increases by 65%—evidence that Root hemoglobins enhance general tissue O2 delivery during acidotic stress. Inhibiting carbonic anhydrase (CA) in the plasma abolished this effect. We argue that CA activity in muscle capillaries short-circuits red blood cell (RBC) pH regulation. This acidifies RBCs, unloads O2 from hemoglobin, and elevates tissue PO2, which could double O2 delivery with no change in perfusion. This previously undescribed mechanism to enhance O2 delivery during stress may represent the incipient function of Root hemoglobins in fishes.

Item ID: 30183
Item Type: Article (Research - C1)
ISSN: 1095-9203
Funders: Natural Sciences and Engineering Research Council of Canada Discovery grant, University of British Columbia, Australian Research Council (ARC)
Date Deposited: 13 Nov 2013 05:27
FoR Codes: 06 BIOLOGICAL SCIENCES > 0603 Evolutionary Biology > 060303 Biological Adaptation @ 40%
06 BIOLOGICAL SCIENCES > 0606 Physiology > 060604 Comparative Physiology @ 20%
06 BIOLOGICAL SCIENCES > 0606 Physiology > 060603 Animal Physiology Systems @ 40%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 100%
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