Mechanism of hydrogen ion transport in the diluting segment of frog kidney |
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Authors: | Hans Oberleithner Florian Lang Georg Messner Wenhui Wang |
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Institution: | (1) Institut für Physiologie, Universität Würzburg, Röntgenring 9, D-8700 Würzburg, Federal Republic of Germany;(2) Universität Innsbruck, Fritz-Preglstr 3, A-6010 Innsbruck, Austria;(3) Harbin Medical College, Harbin, Peoples Republic of China |
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Abstract: | Transepithelial H+ transport was studied in diluting segments of the isolated-perfused kidney ofrana 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 (J
te
H
) as well as limiting transepithelial electrical and H+ electrochemical potential differences (PD
te
,E
te
H
) and luminal pH at zero net flux conditions. The measurements were made in absence (control) and presence of furosemide (5·10–5 mol/l) or amiloride (10–3 mol/l).
E
te
H
(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 correspondingPD
te
-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 secretoryJ
te
H
(from blood to lumen) was found in controls (14±2 pmol·cm–2·S–1) which was stimulated by K+ adaptation (61±8 pmol·cm–2·s–1) but reversed in direction by Na+-adaptation (–8±1 pmol·cm–2·s–1). Amiloride inhibited secretoryJ
te
H
. Elimination of the lumen positivePD
te
by furosemide did not affect significantlyE
te
H
andJ
te
H
in control and K+ adapted animals but abolished reabsorptiveJ
te
H
in Na+ adapted animals.We conclude that in frog diluting segment H+ secretion is an active, amiloride-sensitive, furosemide-insensitive transport process. The data are consistent with luminal Na+/H+ exchange. The activity of this system depends critically on the metabolic state of the animal.Parts of the data were presented at the 16th Ann. Meeting of the Am. Soc. Nephrol., Washington (1983)This work was supported by österr. Forschungsrat, Proj. No.: 4366 and by Dr. Legerlotz Stiftung |
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Keywords: | H+ transport Na+/H+ exchange Amiloride Furosemide Diluting segment Frog kidney |
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