Nucleotide receptors regulate membrane ion transport in renal epithelial cells

John P. Middleton, Allen W. Mangel, Srisaila Basavappa, J. Gregory Fitz

Research output: Contribution to journalArticle

41 Scopus citations

Abstract

Regulation of plasma membrane ion transport by endogenous purinergic receptors was assessed in a distal renal (A6) cell line. Nucleotide analogues stimulated Na-K-Cl cotransport activity with relative potencies of ATP > UTP > ATPγS > 2-methylthio-ATP = α,β-methylene ATP. Activation of nucleotide receptors with extracellular ATP and nucleotide analogues increased intracellular calcium concentration ([Ca2+](i)) primarily by release of intracellular calcium stores, with relative potency of agonists similar to that seen for stimulation of Na-K-Cl cotransport. Neither the change in [Ca2+](i) nor the stimulation of cotransport was abolished by the adenosine receptor antagonist 8-{4-[N-(2-aminoethyl)carbamoylmethoxy]-phenyl}-1,3- dipropylxanthine (XAC). In contrast to the adenosine A2 receptor agonist 5'- N-ethylcarboxamidoadenosine, nucleotide analogues had no discernible effect on cytosolic adenosine 3',5'-cyclic monophosphate levels or adenylyl cyclase activity. To address possible mechanisms for stimulation of Na-K-Cl cotransport by the nucleotide receptor, 125I efflux and patch-clamp studies were used to measure chloride secretion. ATP and ionomycin markedly enhanced 125I efflux and whole cell currents, consistent with activation of chloride conductance pathways. Diphenylamine-2-carboxylate, a chloride channel blocker, eliminated the effects of ionomycin, forskolin, adenosine, and ATP on Na-K-Cl cotransport. This study demonstrates that nucleotide receptors in this model of renal epithelium initiate distinct regulation of Na-K-Cl cotransport. Nucleotide receptors may effect their responses through primary activation of membrane chloride channels.

Original languageEnglish (US)
Pages (from-to)F867-F873
JournalAmerican Journal of Physiology - Renal Fluid and Electrolyte Physiology
Volume264
Issue number5 33-5
DOIs
StatePublished - 1993

Keywords

  • A6 cells
  • chloride channels
  • furosemide
  • purinergic receptors

ASJC Scopus subject areas

  • Physiology

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