title: Inositol 1,4,5-trisphosphate releases Ca2+ from vacuolar membrane vesicles of oat roots.
abstract: In plant cells, transient changes in cytoplasmic Ca2+ levels can modulate numerous developmental processes. Ca2+ is accumulated in the vacuole via a H+/Ca2+ antiport system that is energized by the tonoplast H+-pumping ATPase. Inositol 1,4,5-triphosphate (InsP3), but not inositol 1,4-bisphosphate, myo-inositol 1-phosphate, or fructose 2,6-bisphosphate, caused a transient reduction of Ca2+ levels in tonoplast vesicles. The decrease was dependent on InsP3 concentration (Km apparent = 0.6 microM). The InsP3-induced Ca2+ release was blocked by the Ca2+ antagonist, 8-(N,N-diethylamino)-octyl 3,4,5-trimethoxybenzoate-HCl. These results suggest that the vacuolar membrane is one target site for InsP3 action and that InsP3 may operate as a second messenger in the mobilization of intracellular Ca2+ in plant cells.
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002523:Edible Grain; D004533:Egtazic Acid / Q000494:pharmacology; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000378:metabolism; D009940:Organoids / Q000378:metabolism*; D010944:Plants / Q000648:ultrastructure*; D006180:Proton-Translocating ATPases / Q000378:metabolism; D013403:Sugar Phosphates / Q000494:pharmacology*; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism*
chemical_list: D002121:Calcium Channel Blockers; D007295:Inositol Phosphates; D013403:Sugar Phosphates; D004533:Egtazic Acid; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; D015544:Inositol 1,4,5-Trisphosphate; D006180:Proton-Translocating ATPases; D002118:Calcium