Regulation of intracellular pH in rat renal inner medullary thin limbs of Henle's loop

Thomas L. Pannabecker, Olga H. Brokl, Yung Kyu Kim, Diane E. Abbott, William H. Dantzler

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

Regulation of intracellular pH (pHi) was studied in isolated rat renal inner medullary thin limbs of Henle's loop in bicarbonate/phosphate-buffered medium with high pCO2, high osmolality (≅670 mosmol/kg H2O; 270 mM urea; 180 mM NaCl), organic osmolytes, and a pH of 6.8 to approximate the physiological in vivo environment. The pH-sensitive fluorescent dye 2′,7′-bis(2-carboxyethyl)-5,6-carboxyfluorescein (BCECF) was used to measure pHi. Resting pHi was always acid and significantly more acid in descending thin limb (DTL) cells than in ascending thin limb (ATL) cells from pure or mixed-type thin limbs. Resting pHi was slightly but significantly higher in both DTLs and ATLs in high osmolality (≅670 mosmol/kg H2O) than in low osmolality (≅290 mosmol/kg H2O) medium but not when sucrose replaced urea. In both DTLs and ATLs the rate of recovery of pHi following additional acidification with an NH4Cl pulse was reduced by Na+ removal from the medium and by the addition of 60 μM HOE642 (an inhibitor of the Na+/H+ exchanger, NHE1), 55 μM S1611 (inhibitor of Na+/H+ exchanger, NHE3), 1 μM bafilomycin A1 (an inhibitor of vacuolar H+-ATPase), or 20 μM Schering 28080 (an inhibitor of H+-K+-ATPase) to the medium. Resting pHi was also reduced by 60 μM HOE642, 55 μM S1611, and 20 μM Schering 28080. In both DTLs and ATLs, RT-PCR revealed message for NHE1, NHE3, and vacuolar H+-ATPase; immunocytochemistry demonstrated the expression of the protein for NHE1 (basolateral membrane), NHE3 (luminal membrane), and H+-K+-ATPase (luminal membrane). These data suggest that pHi in rat inner medullary thin limbs is regulated by urea and by basolateral and luminal H+ extrusion via NHE1, NHE3, vacuolar H+-ATPase, and H+-K+-ATPase.

Original languageEnglish (US)
Pages (from-to)446-457
Number of pages12
JournalPflugers Archiv European Journal of Physiology
Volume443
Issue number3
DOIs
StatePublished - Feb 5 2002

Keywords

  • H-ATPase
  • H-K-ATPase
  • Henle's loops
  • Intracellular pH
  • NHE1
  • NHE3
  • Na/H exchange
  • Urea

ASJC Scopus subject areas

  • Physiology
  • Clinical Biochemistry
  • Physiology (medical)

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