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Involvement of the cystic fibrosis transmembrane conductance regulator in the acidosis‐induced efflux of ATP from rat skeletal muscle
Author(s) -
Tu Jie,
Le Gengyun,
Ballard Heather J.
Publication year - 2010
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2010.195255
Subject(s) - cystic fibrosis transmembrane conductance regulator , lactic acid , lactic acidosis , skeletal muscle , intracellular ph , acidosis , medicine , chemistry , endocrinology , efflux , biochemistry , intracellular , biology , cystic fibrosis , bacteria , genetics
The present study was performed to investigate the effect of acidosis on the efflux of ATP from skeletal muscle. Infusion of lactic acid to the perfused hindlimb muscles of anaesthetised rats produced dose‐dependent decreases in pH and increases in the interstitial ATP of extensor digitorum longus (EDL) muscle: 10 m m lactic acid reduced the venous pH from 7.22 ± 0.04 to 6.97 ± 0.02 and increased interstitial ATP from 38 ± 8 to 67 ± 11 n m . The increase in interstitial ATP was well‐correlated with the decrease in pH ( r 2 = 0.93; P < 0.05). Blockade of cellular uptake of lactic acid using α‐cyano‐hydroxycinnamic acid abolished the lactic acid‐induced ATP release, whilst infusion of sodium lactate failed to depress pH or increase interstitial ATP, suggesting that intracellular pH depression, rather than lactate, stimulated the ATP efflux. Incubation of cultured skeletal myoblasts with 10 m m lactic acid significantly increased the accumulation of ATP in the bathing medium from 0.46 ± 0.06 to 0.76 ± 0.08 μ m , confirming the skeletal muscle cells as the source of the released ATP. Acidosis‐induced ATP efflux from the perfused muscle was abolished by CFTR inh ‐172, a specific inhibitor of the cystic fibrosis transmembrane conductance regulator (CFTR), or glibenclamide, an inhibitor of both K ATP channels and CFTR, but it was not affected by atractyloside, an inhibitor of the mitochondrial ATP transporter. Silencing of the CFTR gene using an siRNA abolished the acidosis‐induced increase in ATP release from cultured myoblasts. CFTR expression on skeletal muscle cells was confirmed using immunostaining in the intact muscle and Western blotting in the cultured cells. These data suggest that depression of the intracellular pH of skeletal muscle cells stimulates ATP efflux, and that CFTR plays an important role in the release mechanism.