Norepinephrine-induced Ca2+ waves depend on InsP3 and ryanodine receptor activation in vascular myocytes |
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Authors: | Boittin, Francois-Xavier Macrez, Nathalie Halet, Guillaume Mironneau, Jean |
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Abstract: | In rat portal veinmyocytes, Ca2+ signals can begenerated by inositol 1,4,5-trisphosphate(InsP3)- and ryanodine-sensitive Ca2+ release channels, which arelocated on the same intracellular store. Using a laser scanningconfocal microscope associated with the patch-clamp technique, weshowed that propagated Ca2+ wavesevoked by norepinephrine (in the continuous presence of oxodipine) werecompletely blocked after internal application of ananti-InsP3 receptor antibody.These propagated Ca2+ waves werealso reduced by ~50% and transformed in homogenous Ca2+ responses after applicationof an anti-ryanodine receptor antibody or ryanodine. All-or-noneCa2+ waves obtained withincreasing concentrations of norepinephrine were transformed in adose-response relationship with a Hill coefficient close to unity afterryanodine receptor inhibition. Similar effects of the ryanodinereceptor inhibition were observed on the norepinephrine- andACh-induced Ca2+ responses innon-voltage-clamped portal vein and duodenal myocytes and on thenorepinephrine-induced contraction. Taken together, these results showthat ryanodine-sensitive Ca2+release channels are responsible for the fast propagation of Ca2+ responses evoked by variousneurotransmitters producing InsP3 in vascular and visceral myocytes. |
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