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Calcium release from intracellular stores evoked by extracellular ATP in a X enopus renal epithelial cell line
Author(s) -
Mori Masahiro,
Hosomi Hidenobu,
Nishizaki Tomoyuki,
Kawahara Katsumasa,
Okada Yasuhiro
Publication year - 1997
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.1469-7793.1997.365bk.x
Subject(s) - extracellular , gtp' , guanosine , calcium , intracellular , inositol trisphosphate , biophysics , pertussis toxin , adenosine triphosphate , g protein , chemistry , calcium in biology , microbiology and biotechnology , inositol , biochemistry , biology , signal transduction , receptor , organic chemistry , enzyme
1 The signal transduction mechanism mediating extracellular adenosine 5′‐triphosphate (ATP)‐induced calcium release in a renal epithelial cell line (A6) was investigated using the whole‐cell voltage‐clamp technique and fura‐2 fluorescence measurement. 2 ATP (10 μ M ) activated calcium‐dependent non‐selective cation channels in cells held under voltage clamp. 3 Guanosine 5′‐ O ‐(2‐thiodiphosphate) (GDPβS; 0.1–1.0 m M ) in the pipette inhibited the ATP‐activated calcium‐dependent currents. With guanosine 5′‐ O ‐(3‐thiotriphosphate) (GTPγS; 0.1–1.0 m M ) in the pipette, the currents were spontaneously elicited without application of ATP. Pretreatment with pertussis toxin (PTX) affected neither the ATP‐activated currents nor the increase in intracellular free calcium concentration ([Ca 2+ ]) i evoked by ATP. 4 Intracellular application of neomycin or heparin inhibited the ATP‐activated currents. Inositol 1,4,5‐trisphosphate (IP 3 ; 0.1–100μ M ) in the internal solution produced currents similar to those due to ATP activation. 5 These results suggest that a PTX ‐insensitive guanosine 5′‐triphosphate (GTP)‐binding regulatory protein (G protein) is involved in extracellular ATP‐induced phosphoinositide turnover and subsequent calcium release from IP 3 ‐sensitive stores, which subsequently activates the calcium ‐dependent channels in A6 cells.