Regulation of intracellular pH in the rabbit cortical collecting tubule.
The cortical collecting tubule (CCT) is an important nephron segment for Na+, K+, water and acid-base transport. Differential loading characteristics of the pH sensitive dye 2',7'-bis-(2-carboxyethyl)-5(and-6)carboxyfluorescein (BCECF) and basolateral Cl- removal were used to identify and study intracellular pH (pHi) regulation in each of three cell types involved in this transport. Both principal cells and beta-intercalated cells were found to have a basolateral Na+/H+ exchanger based on the Na+ and amiloride sensitivity of pHi recovery from acid loads. Intercalated cells demonstrated abrupt pHi changes with basolateral Cl- removal. alpha-intercalated cells alkalinized; beta-intercalated cells acidified. In the beta-intercalated cells, luminal Cl- removal blocked changes in pHi in response to changes in luminal HCO3- or peritubular Cl-, providing direct evidence for a luminal Cl-/HCO3- exchanger. In principal cells, brief removal of either peritubular or luminal Cl- resulted in no change in pHi; however, return of peritubular Cl- after prolonged removal resulted in a rapid fall in pHi consistent with a basolateral Cl-/HCO3- exchanger, which may be relatively inactive under baseline conditions. Therefore, Cl-/HCO3- exchange is present in all three cell types but varies in location and activity.
Weiner
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Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
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D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism / Q000494:pharmacology; D005452:Fluoresceins; D005456:Fluorescent Dyes; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007672:Kidney Cortex / Q000187:drug effects / Q000502:physiology*; D007684:Kidney Tubules / Q000502:physiology*; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D009399:Nephrons / Q000502:physiology; D010477:Perfusion; D011817:Rabbits; D012964:Sodium / Q000494:pharmacology; D017923:Sodium-Hydrogen Exchangers
D002352:Carrier Proteins; D002712:Chlorides; D005452:Fluoresceins; D005456:Fluorescent Dyes; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein; D012964:Sodium