Swelling-activated, cystic fibrosis transmembrane conductance regulator-augmented ATP release and Cl- conductances in murine C127 cells.
1. 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 (< or = 80 % osmolality). 2. 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. 3. Gd3+ 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 Gd3+, VSOR Cl- currents were activated normally. 4. 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. 5. 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. 6. 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.
Hazama
A
A
Department of Cellular and Molecular Physiology, National Institute for Physiological Sciences and CREST of Japan Science and Technology Corporation, Okazaki 444-8585, Japan.
Fan
H T
HT
Abdullaev
I
I
Maeno
E
E
Tanaka
S
S
Ando-Akatsuka
Y
Y
Okada
Y
Y
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001081:Apyrase / Q000494:pharmacology; D002712:Chlorides / Q000502:physiology*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism / Q000502:physiology*; D004553:Electric Conductivity; D005682:Gadolinium / Q000494:pharmacology; D005905:Glyburide / Q000494:pharmacology; D006801:Humans; D051379:Mice; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism / Q000473:pathology
C505032:CFTR protein, human; D002712:Chlorides; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000255:Adenosine Triphosphate; D005682:Gadolinium; D001081:Apyrase; D005905:Glyburide