title: V-H+ -ATPase translocation during blood alkalosis in dogfish gills: interaction with carbonic anhydrase and involvement in the postfeeding alkaline tide.
abstract: We investigated the involvement of carbonic anhydrase (CA) in mediating V-H(+)-ATPase translocation into the basolateral membrane in gills of alkalotic Squalus acanthias. Immunolabeling revealed that CA is localized in the same cells as V-H(+)-ATPase. Blood plasma from dogfish injected with acetazolamide [30 mg/kg at time (t) = 0 and 6 h] and infused with NaHCO(3) for 12 h (1,000 microeq.kg(-1).h(-1)) had significantly higher plasma HCO(3)(-) concentration than fish that were infused with NaHCO(3) alone (28.72 +/- 0.41 vs. 6.57 +/- 2.47 mmol/l, n = 3), whereas blood pH was similar in both treatments (8.03 +/- 0.11 vs. 8.04 +/- 0.11 pH units at t = 12 h). CA inhibition impaired V-H(+)-ATPase translocation into the basolateral membrane, as estimated from immunolabeled gill sections and Western blotting on gill cell membranes (0.24 +/- 0.08 vs. 1.00 +/- 0.28 arbitrary units, n = 3; P < 0.05). We investigated V-H(+)-ATPase translocation during a postfeeding alkalosis ("alkaline tide"). Gill samples were taken 24-26 h after dogfish were fed to satiety in a natural-like feeding regime. Immunolabeled gill sections revealed that V-H(+)-ATPase translocated to the basolateral membrane in the postfed fish. Confirming this result, V-H(+)-ATPase abundance was twofold higher in gill cell membranes of the postfed fish than in fasted fish (n = 4-5; P < 0.05). These results indicate that 1) intracellular H(+) or HCO(3)(-) produced by CA (and not blood pH or HCO(3)(-)) is likely the stimulus that triggers the V-H(+)-ATPase translocation into the basolateral membrane in alkalotic fish and 2) V-H(+)-ATPase translocation is important for enhanced HCO(3)(-) secretion during a naturally occurring postfeeding alkalosis.
authors.affiliation: Dept of Biological Sciences, Univ of Alberta, Edmonton, Alberta, Canada. martint@ualberta.ca
authors.forename: Martin
authors.initials: M
authors.lastname: Tresguerres
authors.forename: Scott K
authors.initials: SK
authors.lastname: Parks
authors.forename: Chris M
authors.initials: CM
authors.lastname: Wood
authors.forename: Greg G
authors.initials: GG
authors.lastname: Goss
mesh_terms: D000471:Alkalosis / Q000097:blood*; D000818:Animals; D002256:Carbonic Anhydrases / Q000378:metabolism*; D004284:Dogfish / Q000097:blood / Q000378:metabolism*; D005247:Feeding Behavior / Q000502:physiology; D005880:Gills / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D019518:Postprandial Period / Q000502:physiology*; D021381:Protein Transport; D017693:Sodium Bicarbonate / Q000494:pharmacology; D013997:Time Factors; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism*
chemical_list: D017693:Sodium Bicarbonate; D025262:Vacuolar Proton-Translocating ATPases; D002256:Carbonic Anhydrases