title: White sturgeon (Acipenser transmontanus) acid-base regulation differs in response to different types of acidoses.
abstract: White sturgeon (Acipenser transmontanus) completely protect intracellular tissue pH (pHi) despite large reductions in extracellular (blood) pH (pHe), termed preferential pHiregulation, in response to elevated environmental PCO2(hypercarbia) and in general appear to be relatively resilient to stressors. Preferential pHiregulation is thought to be associated with hypercarbia tolerance in general, but has also recently been observed to protect pHiagainst metabolic acidoses induced by exhaustive exercise and anoxia in a tropical air breathing catfish. We hypothesized that preferential pHiregulation may also be a general strategy of acid-base regulation in sturgeon. To address this hypothesis, severe acidoses were imposed to reduce pHe, and the presence or absence of preferential pHiregulation was assessed in red blood cells (RBC), heart, brain, liver and white muscle. A respiratory acidosis was imposed using hyperoxia, while metabolic acidoses were induced by exhaustive exercise, anoxia or air exposure. Reductions in pHeoccurred following hyperoxia (0.15 units), exhaustive exercise (0.30 units), anoxia (0.10 units) and air exposure (0.35 units); all acidoses reduced RBC pHi. Following hyperoxia, heart, brain and liver pHiwere preferentially regulated against the reduction in pHe, similar to hypercarbia exposure. Following all metabolic acidoses heart pHiwas protected and brain pHiremained unchanged following exhaustive exercise and air exposure, however, brain pHiwas reduced following anoxia. Liver and white muscle pHiwere reduced following all metabolic acidoses. These results suggest preferential pHiregulation may be a general strategy during respiratory acidoses but during metabolic acidoses, the response differs between source of acidoses and tissues.
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, BC, Canada. shartau@zoology.ubc.ca.
authors.forename: Ryan B
authors.initials: RB
authors.lastname: Shartau
authors.affiliation: Department of Fisheries and Aquaculture, Vancouver Island University, Nanaimo, BC, Canada.
authors.forename: Dan W
authors.initials: DW
authors.lastname: Baker
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Brauner
mesh_terms: D000136:Acid-Base Equilibrium; D000140:Acidosis, Lactic / Q000097:blood*; D000142:Acidosis, Respiratory / Q000097:blood*; D000818:Animals; D001921:Brain / Q000378:metabolism; D002245:Carbon Dioxide / Q000097:blood; D002712:Chlorides / Q000097:blood; D004912:Erythrocytes / Q000378:metabolism; D005399:Fishes / Q000097:blood*; D006400:Hematocrit; D006863:Hydrogen-Ion Concentration; D018496:Hyperoxia / Q000097:blood; D000860:Hypoxia / Q000097:blood; D019344:Lactic Acid / Q000097:blood; D008099:Liver / Q000378:metabolism; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D005082:Physical Exertion; D013997:Time Factors
chemical_list: D002712:Chlorides; D002245:Carbon Dioxide; D019344:Lactic Acid
keywords: Acid–base regulation; Acipenser transmontanus; Fish; Preferential pHi regulation; Sturgeon