title: Evidence for OH-/H+ permeation across the peritubular cell membrane of rat renal proximal tubule in HCO3(-)-free solutions.
abstract: Membrane potentials and intracellular pH were measured on rat renal proximal tubular cells in vivo to test whether sodium-bicarbonate cotransport across the peritubular cell membrane accepts OH- (or H+ in opposite direction) or whether it requires the CO2, HCO3-, CO3= buffer to operate. It was found that step changes of peritubular pH in nominally HCO3(-)-free and CO2-free solutions produced qualitatively similar initial potential responses and cell pH responses as changes in peritubular HCO3- concentrations. These responses, however, were considerably smaller and they were neither reduced in Na+-free solutions nor inhibited by the stilbene derivative SITS which is known to block Na+ (HCO3-)n cotransport completely. We conclude that the cotransporter requires the CO2, HCO3-, CO3= buffer for its physiological operation but that high rates of OH- or H+ can also be transferred across the peritubular cell membrane in HCO3(-)-free solutions, probably through a separate transport system.
mesh_terms: D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D001639:Bicarbonates / Q000378:metabolism* / Q000502:physiology; D001692:Biological Transport / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D011522:Protons; D051381:Rats; D012964:Sodium / Q000378:metabolism* / Q000502:physiology; D017693:Sodium Bicarbonate
chemical_list: D001639:Bicarbonates; D006878:Hydroxides; D011522:Protons; D001464:Barium; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D017693:Sodium Bicarbonate; D012964:Sodium