title: Low oxygen cost of carbonic anhydrase-dependent sodium reabsorption in the dog kidney.
abstract: To examine the oxygen requirement of carbonic anhydrase-dependent sodium reabsorption in the proximal tubule, 18 anaesthetized dogs were studied under conditions of saturated distal NaCl reabsorption; the latter was accomplished by volume expansion (all groups) combined with infusion of loop diuretics (groups 1 and 3). Acetazolamide reduced HCO3- reabsorption by 602 +/- 32 mumol min-1 (55%, group 1) and by 777 +/- 103 mumol min-1 (66%, group 2). This was accompanied with a reduction in sodium reabsorption and oxygen consumption in a molar delta Na/delta O2 ratio of about 45 in both groups of dogs. The delta HCO3/delta O2 ratio averaged 16 +/- 1, which was not significantly different from the theoretical value of 18 expected for transcellular sodium transport by Na+, K+-ATPase. Mannitol (group 3) reduced NaCl reabsorption by 37 +/- 2% without affecting NaHCO3 reabsorption or oxygen consumption significantly. We conclude that carbonic anhydrase-dependent NaCl reabsorption in the proximal tubules is passive, and that NaHCO3 reabsorption is the only important active sodium transport which is sensitive to inhibition of carbonic anhydrase.
authors.affiliation: Institute for Experimental Medical Research, University of Oslo, Ullevaal Hospital, Norway.
authors.forename: J
authors.initials: J
authors.lastname: Ostensen
authors.forename: E S
authors.initials: ES
authors.lastname: Stokke
authors.forename: A
authors.initials: A
authors.lastname: Hartmann
authors.forename: K
authors.initials: K
authors.lastname: Wensell
authors.forename: F
authors.initials: F
authors.lastname: Kiil
mesh_terms: D000086:Acetazolamide / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D002256:Carbonic Anhydrases / Q000378:metabolism*; D004234:Diuretics, Osmotic / Q000494:pharmacology; D004285:Dogs; D005260:Female; D005919:Glomerular Filtration Rate / Q000187:drug effects; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D008353:Mannitol / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects; D012965:Sodium Chloride / Q000378:metabolism*; D014882:Water-Electrolyte Balance / Q000187:drug effects
chemical_list: D001639:Bicarbonates; D004234:Diuretics, Osmotic; D008353:Mannitol; D012965:Sodium Chloride; D002256:Carbonic Anhydrases; D000086:Acetazolamide