Acidosis

Scientists at University of British Columbia publish new data on physiology

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"Am J Physiol Regul Integr Comp Physiol 296: R1868-R1880, 2009. First published April 1, 2009; doi:10.1152/ajpregu.90767.2008.-Sturgeons are among the most CO2 tolerant of fishes investigated to date. However, the basis of this exceptional CO2 tolerance is unknown. Here, white sturgeon, Acipenser transmontanus, were exposed to elevated CO2 to investigate the mechanisms associated with short-term hypercarbia tolerance. During exposure to 1.5 kPa PCO2, transient blood pH [extracellular pH (pHe)] depression was compensated within 24 h and associated with net plasma HCO3- accumulation and equimolar Cl- loss, and changes in gill morphology, such as a decrease in apical surface area of mitochondrial-rich cells. These findings indicate that pHe recovery at this level of hypercarbia is accomplished in a manner similar to most freshwater teleost species studied to date, although branchial mechanisms involved may differ. White sturgeon exposed to more severe hypercarbia (3 and 6 kPa PCO2) for 48 h exhibited incomplete pH compensation in blood and red blood cells. Despite pHe depression, intracellular pH (pHi) of white muscle, heart, brain, and liver did not decrease during a transient (6 h of 1.5 kPa PCO2) or prolonged (48 h at 3 and 6 kPa PCO2) blood acidosis. This pHi protection was not due to high intrinsic buffering in tissues. Such tight active cellular regulation of pHi in the absence of pHe compensation represents a unique pattern for non-air-breathing fishes, and we hypothesize that it is the basis for the exceptional CO2 tolerance of white sturgeon and, likely, other CO2 tolerant fishes," wrote D.W. Baker and colleagues, University of British Columbia.

The researchers concluded: "Further research to elucidate the specific mechanisms responsible for this tremendous pH regulatory capacity in tissues of white sturgeon is warranted."

Baker and colleagues published the results of their research in American Journal of Physiology - Regulatory Integrative and Comparative Physiology (Complete intracellular pH protection during extracellular pH depression is associated with hypercarbia tolerance in white sturgeon, Acipenser transmontanus. American Journal of Physiology - Regulatory Integrative and Comparative Physiology, 2009;296(6):R1868-R1880).

For additional information, contact D.W. Baker, University of British Columbia, Dept. of Zoology, 6270 University Blvd., Vancouver, BC V6T 1Z4, Canada.

The publisher of the American Journal of Physiology - Regulatory Integrative and Comparative Physiology can be contacted at: American Physiological Society, 9650 Rockville Pike, Bethesda, MD 20814, USA.

Keywords: Canada, Vancouver, Comparative Physiology, Hypercapnia, University of British Columbia.

This article was prepared by Life Science Weekly editors from staff and other reports. Copyright 2009, Life Science Weekly via NewsRx.com.