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Swelling‐activated, cystic fibrosis transmembrane conductance regulator‐augmented ATP release and Cl − conductances in murine C127 cells
Author(s) -
Hazama Akihiro,
Fan HaiTian,
Abdullaev Iskandar,
Maeno Emi,
Tanaka Shoko,
AndoAkatsuka Yuhko,
Okada Yasunobu
Publication year - 2000
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 - 10.1111/j.1469-7793.2000.t01-6-00001.x
Subject(s) - cystic fibrosis transmembrane conductance regulator , apyrase , chloride channel , chemistry , dids , biophysics , tonicity , intracellular , patch clamp , glibenclamide , microbiology and biotechnology , biochemistry , extracellular , biology , membrane , endocrinology , receptor , gene , diabetes mellitus
A hypotonic challenge, but not cAMP stimulation, was found to induce release of ATP measured by the luciferin‐luciferase assay from both the murine mammary carcinoma cell line C127i and C127 cells stably transfected with the cDNA for human cystic fibrosis transmembrane conductance regulator (CFTR) protein (C127/CFTR). CFTR expression augmented swelling‐induced ATP release by 10–20 times under hypotonic conditions (<= 80 % osmolality). Glibenclamide failed to suppress swelling‐induced ATP release from C127/CFTR cells. In contrast, whole‐cell patch‐clamp recordings showed that both the cAMP‐activated ohmic Cl − currents and volume‐sensitive outwardly rectifying (VSOR) Cl − currents were prominently suppressed by glibenclamide. Gd 3+ markedly blocked swelling‐induced ATP release but failed to suppress both cAMP‐ and swelling‐activated Cl − currents in the CFTR‐expressing cells. Even after pretreatment and during treatment with Gd 3+ , VSOR Cl − currents were activated normally. The continuous presence of an ATP‐hydrolysing enzyme, apyrase, in the bathing solution did not prevent activation of VSOR Cl − currents in C127/CFTR cells. The rate of regulatory volume decrease (RVD) in C127/CFTR cells was much faster than that in C127i cells. When apyrase was added to the bathing solution, the RVD rate was retarded in C127/CFTR cells. On balance, the following conclusions can be deduced. First, swelling‐induced ATP release is augmented by expression of CFTR but is not mediated by the CFTR Cl − channel. Second, swelling‐induced ATP release is not mediated by the VSOR Cl − channel. Third, the released ATP facilitated the RVD process but is not involved in the activation of VSOR Cl − channels in C127/CFTR cells.