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Coupling between H+ transport and anaerobic glycolysis in turtle urinary bladder: effects of inhibitors of H+ ATPase

par Steinmetz, Philip R.;Husted, Russell F.;Beauwens, Renaud ;Mueller, Allan
Référence The journal of membrane biology, 59, 1, page (27-34)
Publication Publié, 1981-03

Article révisé par les pairs

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Résumé :

The coupling between H+ transport (JH) and anaerobic glycolysis was examined in vitro in an anaerobic preparation of turtle urinary bladder. JH was measured as the short-circuit current after Na+ transport was abolished with ouabain and by pH stat titration. The media were gassed with N2 and 1% CO2 (PO2<0.5 mm Hg) and contained 10 mm glucose. Under these conditions, JH was not inhibited by 3 mm serosal (S) cyanide or by 0.1 mm mucosal (M) dinitrophenol. Control anerobic lactate production (Jlac) of 47 bladders was plotted as a function of simultaneously measured JH. The slope of Jlac on JH was 0.58±0.12 with an intercept for Jlac at JH=0 of 0.55 μmol/hr. Values for δJlac/δJH were determined in groups of individual bladders when JH was inhibited by an opposing pH gradient (0.55±0.16), by acetazolamide (0.58±0.19) and by dicyclohexylcarbodiimide, DCCD (0.58±0.14). The constancy of δJlac/δJH indicates a high degree of coupling between JH and Jlac. Since the anaerobic metabolism of glucose produces one ATP for each lactate formed, the δJlac/δJH values can be used to estimate the stoichiometry of H+ translocation. The movement of slightly less than 2 H+ ions is coupled to the hydrolysis of one ATP. During anaerobiosis (absence of mitochondrial ATPase function) the acidification pump was not inhibited by M addition of oligomycin but was inhibited by M addition of DCCD and Dio-9, inhibitors of H+ flow in the proteolipid portion of H+-translocating ATPases. DCCD inhibited anaerobic JH without change in δJlac/δJH or basal Jlac and, therefore, acted primarily on the H+ pump. S addition of vanadate also inhibited JH, but the inhibition was associated with an increase in Jlac. The site of this apparent uncoupling remains to be defined. The acidification pump of the luminal cell membrane of the turtle bladder has H+-ATPase characteristics that differ from mitochondrial ATPase in that H+ transport is oligomycin-resistant and vanadate-sensitive. As judged from the flows of H+ and lactate, the H+/ATP stoichiometry of the pump is about 2. © 1981 Springer-Verlag New York Inc.