Calcium release from intracellular stores evoked by extracellular ATP in a Xenopus renal epithelial cell line.
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 microM) activated calcium-dependent non-selective cation channels in cells held under voltage clamp. 3. Guanosine 5'-O-(2-thiodiphosphate) (GDP beta S; 0.1-1.0 mM) in the pipette inhibited the ATP-activated calcium-dependent currents. With guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S; 0.1-1.0 mM) 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 ([Ca2+]i) evoked by ATP. 4. Intracellular application of neomycin or heparin inhibited the ATP-activated currents. Inositol 1,4,5-trisphosphate (IP3; 0.1-100 microM) 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 IP3-sensitive stores, which subsequently activates the calcium-dependent channels in A6 cells.
Mori
M
M
Department of Physiology, Kobe University, School of Medicine, Japan. mm@med.kobe-u.ac.jp
Hosomi
H
H
Nishizaki
T
T
Kawahara
K
K
Okada
Y
Y
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D004533:Egtazic Acid / Q000494:pharmacology; D004848:Epithelium / Q000187:drug effects / Q000502:physiology; D016257:Fura-2; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007668:Kidney / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008856:Microscopy, Fluorescence; D009355:Neomycin / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D037342:Pertussis Toxin; D015398:Signal Transduction / Q000187:drug effects; D013873:Thionucleotides / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D014981:Xenopus
D013873:Thionucleotides; D010566:Virulence Factors, Bordetella; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D004533:Egtazic Acid; C023427:guanosine 5'-O-(2-thiodiphosphate); D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D006493:Heparin; D037342:Pertussis Toxin; D009355:Neomycin; D002118:Calcium; D016257:Fura-2