Ca2+ depletion and inositol 1,4,5-trisphosphate-evoked activation of Ca2+ entry in single guinea pig hepatocytes.
Store-operated Ca(2+) entry was investigated by monitoring the Ca(2+)-dependent K(+) permeability in voltage-clamped guinea pig hepatocytes. In physiological conditions, intracellular Ca(2+) stores are discharged following agonist stimulation, but depletion of this stores can be achieved using Ca(2+)-Mg(2+)-ATPase inhibitors such as 2,5-di(tert-butyl)-1,4-benzohydroquinone and thapsigargin. The effect of internal Ca(2+) store depletion on Ca(2+) influx was tested in single cells using inositol 1,4,5-trisphosphate (InsP(3)) release from caged InsP(3) after treatment of the cells with 2, 5-di(tert-butyl)-1,4-benzohydroquinone or thapsigargin in Ca(2+)-free solutions. We show that the photolytic release of 1-d-myo-inositol 1,4-bisphosphate 5-phosphorothioate, a stable analog of InsP(3), and Ca(2+) store depletion have additive effects to activate a high level of Ca(2+) entry in single guinea pig hepatocytes. These results suggest that there is a direct functional interaction between InsP(3) receptors and Ca(2+) channels in the plasma membrane, although the nature of these Ca(2+) channels in hepatocytes is unclear.
Guihard
G
G
INSERM U442, Université Paris-Sud, Bât. 443, 91405 Orsay, France.
Noel
J
J
Capiod
T
T
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002478:Cells, Cultured; D006168:Guinea Pigs; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D017136:Ion Transport; D008099:Liver / Q000378:metabolism*; D018408:Patch-Clamp Techniques
D015220:Calcium Channels; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium