title: Intracellular pH regulation in cultured renal proximal tubule cells in different stages of maturation.
abstract: This study examines the ontogeny of cellular pH regulation in renal proximal tubule cells (RPTC). RPTC from 8- to 40-day-old Sprague-Dawley rats (RPTC-8 to RPTC-40) were studied after 48 h of primary culture. Intracellular pH (pHi) was measured by quantitative fluorescence microscopy using 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. Recordings were made under basal conditions and after imposing a cytoplasmic alkalosis and acidosis using 15 mM NH4+ salt. The net recovery rate (dpHi/dt) from intracellular acidosis increases significantly between 10 and 12 days of age from 0.39 +/- 0.04 to 0.54 +/- 0.06 pH units/min (P < 0.05, n = 10 vs. 6). This increase can be completely accounted for by an increase in the rate of amiloride (100 microM)-inhibitable Na(+)-H+ exchange (0.29 +/- 0.04 vs. 0.42 +/- 0.05 pH units/min, P < 0.05, n = 6 vs. 6). The rate of Na(+)-H+ exchange increases similarly in RPTC-10 and RPTC-40 when the transmembrane Na+ gradient is increased by Na+ depleting the cells (48 and 49%, respectively). The amiloride-insensitive recovery is Na+ independent and insensitive to 4-acetamido-4'-isothiocyanostilbene-2-2'-disulfonic acid (SITS, 500 microM) (range 0.08-0.14 pH units/min). The net recovery rate from intracellular alkalosis is significantly lower in RPTC-10 than in RPTC-40 (0.16 +/- 0.02 vs. 0.28 +/- 0.02 pH units/min, P < 0.01, n = 4 vs. 5). SITS (500 microM) inhibits the recovery by 27 +/- 8 and 26 +/- 9%, respectively, whereas amiloride has no effect.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pediatrics, St. Göran's Children's Hospital, Karolinska Institute, Stockholm, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Ekblad
authors.forename: A
authors.initials: A
authors.lastname: Aperia
authors.forename: S H
authors.initials: SH
authors.lastname: Larsson
mesh_terms: D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000143:Acids / Q000494:pharmacology; D000375:Aging / Q000378:metabolism*; D000468:Alkalies / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002478:Cells, Cultured; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017923:Sodium-Hydrogen Exchangers
chemical_list: D000143:Acids; D000468:Alkalies; D002352:Carrier Proteins; D017923:Sodium-Hydrogen Exchangers; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D000584:Amiloride