title: Mechanism of hydrogen ion transport in the diluting segment of frog kidney.
abstract: Transepithelial H+ transport was studied in diluting segments of the isolated-perfused kidney of rana esculenta. The experiments were performed in controls as well as in K+-adapted and Na+-adapted animals (exposed to 50 mmol/l KCl or NaCl, resp. for at least 3 days). Conventional and single-barreled, liquid ion-exchanger H+-sensitive microelectrodes were applied in the tubule lumen to evaluate transepithelial H+ net flux (JHte) as well as limiting transepithelial electrical and H+ electrochemical potential differences (PDte, EHte) and luminal pH at zero net flux conditions. The measurements were made in absence (control) and presence of furosemide (5 X 10(-5) mol/l) or amiloride (10(-3) mol/l). EHte (lumen positive vs ground) was 19 +/- 3 mV in controls, 43 +/- 3 mV in K+ adapted but about zero in Na+ adapted animals. Using the corresponding PDte-values, steady state luminal pH of 7.63 +/- 0.05, 7.13 +/- 0.05 and 8.02 +/- 0.02 was calculated for the respective groups of animals (peritubular pH 7.80). In parallel, significant secretory JHte (from blood to lumen) was found in controls (14 +/- 2 pmol X cm-2 X s-1) which was stimulated by K+ adaptation (61 +/- 8 pmol X cm-2 X s-1) but reversed in direction by Na+-adaptation (-8 +/- 1 pmol X cm-2 X s-1). Amiloride inhibited secretory JHte.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000136:Acid-Base Equilibrium / Q000187:drug effects; D000450:Aldosterone / Q000502:physiology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002463:Cell Membrane Permeability / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D007684:Kidney Tubules / Q000502:physiology*; D007686:Kidney Tubules, Distal / Q000502:physiology*; D011188:Potassium / Q000378:metabolism; D011522:Protons; D011893:Rana esculenta; D012964:Sodium / Q000378:metabolism
chemical_list: D011522:Protons; D000450:Aldosterone; D000584:Amiloride; D012964:Sodium; D011188:Potassium