Relationship between HCO3- transport and oxidative metabolism in rabbit proximal tubule.
HCO3-/CO2 can affect proximal tubule energy metabolism directly by serving as a substrate for metabolic reactions and indirectly through ATP utilization by HCO3(-)-coupled Na+ reabsorption and proton secretion. In this study, metabolic and transport roles of HCO3-/CO2 were examined by measuring the effects of HCO3-/CO2 removal and transport inhibitors on oxygen consumption (QO2) in suspensions of rabbit proximal tubules. Removal of medium HCO3-/CO2 inhibited ouabain-sensitive, ouabain-insensitive, and uncoupled QO2. Consistent with metabolic inhibition, the absence of HCO3-/CO2 also reduced tubule ATP content and stimulated lactate production. Analysis of the dependence of mitochondrial state 3 respiration on HCO3-/CO2 in digitonin-permeabilized tubules traced the metabolic inhibition to limitations in tricarboxylic acid cycle intermediate supply. Energy requirements for HCO3- transport were examined by measuring QO2 in response to acetazolamide, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS), and the H(+)-adenosinetriphosphatase (H(+)-ATPase) inhibitor bafilomycin A. Acetazolamide had no effect on QO2, whereas DIDS-SITS and bafilomycin A reduced ouabain-insensitive QO2, consistent with inhibition of active proton secretion. DIDS-SITS did not affect ouabain-sensitive respiration, suggesting that HCO3(-)-dependent Na+ reabsorption may not be mediated through the Na(+)-K(+)-ATPase in this preparation.
Dickman
K G
KG
Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710.
Mandel
L J
LJ
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D027321:Anion Transport Proteins; D001639:Bicarbonates / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D002245:Carbon Dioxide / Q000378:metabolism; D002352:Carrier Proteins / Q000037:antagonists & inhibitors; D002952:Citric Acid Cycle; D005260:Female; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology; D010084:Oxidation-Reduction / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D011817:Rabbits; D012964:Sodium / Q000378:metabolism
D027321:Anion Transport Proteins; D001639:Bicarbonates; D002352:Carrier Proteins; D002245:Carbon Dioxide; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D010042:Ouabain; D000255:Adenosine Triphosphate; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid