title: Amiloride-sensitive Na+/H+ antiporter in basolateral membrane of hamster ascending thin limb of Henle's loop.
abstract: The mechanisms of intracellular pH (pHi) regulation were investigated in the in vitro microperfused hamster ascending thin limb (ATL) of Henle's loop with the fluorescent pH indicator, 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. pHi of ATL cells was 7.05 +/- 0.02 (n = 30) when microperfused with a CO2/HCO(3-)-buffered solution. In HEPES-buffered solution, pHi was 7.10 +/- 0.02 (n = 16), which was significantly higher than the value in CO2/HCO(3-)-buffered solution (P < 0.05, n = 16). In HEPES-buffered solution, elimination of Na+ and addition of 1 mM amiloride to basolateral solution decreased the pHi by 0.12 +/- 0.03 (n = 6) and 0.11 +/- 0.02 (n = 5) at 1 min, respectively. The same manipulations in the luminal solution had no effect on pHi. One millimolar of N-ethylmaleimide (NEM) added to either side of ATL caused no significant change in pHi. Elimination of K+ on either side of ATL did not alter pHi. After adding 20 mM NH4Cl to basolateral solution, pHi instantaneously increased from 7.17 +/- 0.01 to 7.51 +/- 0.03 (n = 3), and then returned to steady-state level of 7.21 +/- 0.05 (n = 15) in 3 min. Removal of NH4Cl from basolateral solution then caused a rapid fall in pHi to 6.31 +/- 0.05 (n = 15), followed by spontaneous recovery at a rate of 0.43 +/- 0.06 unit/min (n = 15).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pediatrics, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Fujiwara
authors.forename: Y
authors.initials: Y
authors.lastname: Kondo
authors.forename: Y
authors.initials: Y
authors.lastname: Igarashi
authors.forename: C N
authors.initials: CN
authors.lastname: Inoue
authors.forename: N
authors.initials: N
authors.lastname: Takahashi
authors.forename: K
authors.initials: K
authors.lastname: Tada
authors.forename: K
authors.initials: K
authors.lastname: Abe
mesh_terms: D000584:Amiloride / Q000494:pharmacology*; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D006224:Cricetinae; D005033:Ethylmaleimide / Q000494:pharmacology; D005452:Fluoresceins; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D008138:Loop of Henle / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D008647:Mesocricetus; D010477:Perfusion; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*
chemical_list: D005452:Fluoresceins; D017923:Sodium-Hydrogen Exchangers; D000643:Ammonium Chloride; D000584:Amiloride; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein; D005033:Ethylmaleimide