TY - JOUR
T1 - Nucleotide receptors regulate membrane ion transport in renal epithelial cells
AU - Middleton, John P.
AU - Mangel, Allen W.
AU - Basavappa, Srisaila
AU - Fitz, J. Gregory
PY - 1993
Y1 - 1993
N2 - 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.
AB - 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.
KW - A6 cells
KW - chloride channels
KW - furosemide
KW - purinergic receptors
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U2 - 10.1152/ajprenal.1993.264.5.f867
DO - 10.1152/ajprenal.1993.264.5.f867
M3 - Article
C2 - 8388653
AN - SCOPUS:0027174730
VL - 264
SP - F867-F873
JO - American Journal of Physiology - Heart and Circulatory Physiology
JF - American Journal of Physiology - Heart and Circulatory Physiology
SN - 0363-6135
IS - 5 33-5
ER -