Madin-Darby canine kidney cells. II. Aldosterone stimulates Na+/H+ and Cl-/HCO3- exchange.
Experiments in dome epithelium of Madin-Darby canine kidney (MDCK) cells were performed to elucidate aldosterone action on acid-base transport. By means of pH-sensitive microelectrodes the pH of the dome fluid was measured while the apical plasma membrane was superfused. In the absence of HCO3- the dome fluid (facing the basolateral cell membrane) alkalinized in response to 10(-7) mol/l aldosterone. Amiloride (10(-3) mol/l) inhibited dome formation and pH recovery of the dome fluid from an extracellular acid load. In the presence of HCO3- dome fluid acidified in response to aldosterone. The stilbene derivative diisothiocyanate-stilbene-2,2'-disulphonic acid (DIDS) or removal of Cl- from the apical perfusate inhibited this dome acidification. In aldosterone-depleted MDCK monolayers HCO3- was actively accumulated in the dome fluid in contrast to aldosterone-supplemented cells. The results indicate that aldosterone stimulates both amiloride-sensitive Na+/H+ exchange and DIDS-sensitive Cl-/HCO3- exchange in the apical cell membrane of MDCK cells. In the absence of aldosterone the HCO3- extrusion process is localized in the basolateral membrane in series with apical Na+/H+ exchange, while in the presence of aldosterone Cl-/HCO3- is mainly localized in the apical membrane in parallel with Na+/H+ exchange. Cl- exits the cell through apical Cl- channels and is absorbed via the paracellular route.
Oberleithner
H
H
Department of Physiology, University of Würzburg, Federal Republic of Germany.
Vogel
U
U
Kersting
U
U
Steigner
W
W
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000450:Aldosterone / Q000494:pharmacology*; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides / Q000494:pharmacology; D004285:Dogs; D004553:Electric Conductivity; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers
D001639:Bicarbonates; D002352:Carrier Proteins; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides; D017923:Sodium-Hydrogen Exchangers; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D000450:Aldosterone; D000584:Amiloride; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid