Neonatal rabbit proximal tubule basolateral membrane Na+/H+ antiporter and Cl-/base exchange

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15 Scopus citations

Abstract

The present in vitro microperfusion study examined the maturation of Na+/H+ antiporter and Cl-/base exchanger on the basolateral membrane of rabbit superficial proximal straight tubules (PST). Intracellular pH (pH(i)) was measured with the pH-sensitive fluorescent dye 2',7'-bis(2-carboxyethyl)- 5(6)-carboxyfluorescein in neonatal and adult superficial PST. Na+/H+ antiporter activity was examined after basolateral Na+ addition in tubules initially perfused and bathed without Na+. Neonatal Na+/H+ antiporter activity was ~40% that of adult segment (9.7 ± 1.5 vs. 23.7 ± 3.2 pmol · mm-1 · min-1; p < 0.001). The effect of bath Cl- removal on pH(i) was used to assess the rates of basolateral Cl-/base exchange. In both neonatal and adult PST, the Cl-/base exchange activity was significantly higher in the presence of 25 mM HCO3 than in the absence of HCO3 and was inhibited by cyanide and acetazolamide, consistent with Cl-/HCO3 exchange. The proton flux rates in the presence of bicarbonate in neonatal and adult tubules were 14.1 ± 3.6 and 19.5 ± 3.5 pmol. mm-1 min-1, respectively (P = NS), consistent with a mature rate of Cl-/HCO3 exchanger activity in neonatal tubules. Basolateral Cl-/base exchange activity in the absence of CO2 and HCO3, with luminal and bath cyanide and acetazolamide, was greater in adult than in neonatal PST and inhibited by bath DIDS consistent with a maturational increase in Cl-/OH- exchange. We have previously shown that the rates of the apical membrane Na+/H+ antiporter and Cl-/base exchanger were approximately fivefold lower in neonatal compared with adult rabbit superficial PST. These data demonstrate that neonatal PST basolateral membrane Na+/H+ antiporter and Cl-/base exchanger activities are relatively more mature than the Na+/H+ antiporter and Cl-/base exchangers on the apical membrane.

Original languageEnglish (US)
Pages (from-to)R1792-R1797
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume276
Issue number6 45-6
StatePublished - Jun 1 1999

Keywords

  • Cl/HCO/ exchanger
  • Cl/OH exchanger
  • Intracellular pH
  • Microperfusion
  • Na-bicarbonate cotransporter
  • Renal development

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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