| Autor: |
Missiaen, Ludwig, De Smedt, Humbert, Parys, Jan B., Van Acker, Kristel, De Smet, Patrick, Callewaert, Geert |
| Zdroj: |
Biochemical and Biophysical Research Communications; November 1999, Vol. 264 Issue: 3 p967-971, 5p |
| Abstrakt: |
It is still debated whether inositol 1,4,5-trisphosphate(IP3)-induced Ca2+release is loading-dependent. We now report that stimulation of the IP3receptor by luminal Ca2+depends on the cytosolic [Ca2+] in permeabilized A7r5 cells. The EC50and maximal extent of Ca2+release were loading-dependent in the presence of 5 mM 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid: the EC50increased 1.9-fold and the maximal release decreased from 88 to 52% when the stores contained 73% less Ca2+. In the presence of 0.3 μM free Ca2+, the EC50for filled and less filled stores differed, however, only 1.2-fold and the maximal Ca2+release was respectively 96 and 87% of the total releasable Ca2+. At 1 μM free Ca2+, the difference in EC50between filled and less filled stores again became larger (2.2-fold)and the maximal Ca2+release decreased from 93 to 87% when the stores contained less Ca2+. |
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