Basolateral regulation of pHi in proximal tubules of avian loopless and long-looped nephrons in bicarbonate.
In isolated, nonperfused chicken proximal tubules from both loopless reptilian-type and long-looped mammalian-type nephrons, resting intracellular pH (pHi), measured with pH-sensitive fluorescent dye 2',7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein (BCECF), was approximately 7.1 under control HCO3- conditions [20 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES)/5 mM HCO3(-)-buffered medium with pH 7.4 at 37 degrees C] and was reduced to approximately 6.8 in response to NH4Cl pulse. The rate of recovery of pHi (dpHi/dt) from this level to the resting level in proximal tubules from both nephron types was (1) significantly reduced by the removal of Na+ or both Na+ and Cl- from the bath, and (2) unaffected by the removal of Cl- from the bath or the presence of a high K+ concentration or Ba2+ in the bath. In proximal tubules from long-looped mammalian-type, but not loopless reptilian-type, nephrons, dpHi/dt was significantly reduced by the addition of either 5-(N-ethyl-N-isopropyl) amiloride (EIPA) or 4,4'-diisothiocyanostilbene-2,2'disulfonate (DIDS) to the bath. These data suggest that a Na+/H+ exchanger and most likely a Na(+)-dependent Cl-/HCO3- exchanger are involved in basolateral regulation of pHi in mammalian-type nephrons whereas none of the commonly identified basolateral acid-base transporters appear to be involved in regulation of pHi in reptilian-type nephrons.
Department of Physiology, College of Medicine, University of Arizona, Tucson 85725-5051, USA.
O H
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Brokl
C L
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Martinez
Y K
YK
Kim
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Abbott
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Dantzler
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000641:Ammonia / Q000494:pharmacology; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D001639:Bicarbonates / Q000378:metabolism*; D002645:Chickens / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D005260:Female; D006863:Hydrogen-Ion Concentration; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism
D001639:Bicarbonates; D002712:Chlorides; D000643:Ammonium Chloride; D001464:Barium; D000641:Ammonia; D000584:Amiloride; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium; C039614:ethylisopropylamiloride