title: Release of Ca2+ from plant hypocotyl microsomes by inositol-1,4,5-trisphosphate.
abstract: The effect of inositol-1,4,5-trisphosphate on Ca2+ release from microsomes isolated from dark-grown zucchini (Cucurbita pepo L.) hypocotyls was studied. Up to 30% of the Ca2+ taken up by the microsomes in the presence of 2mM ATP, was released by mumolar concentrations of inositol-1,4, 5-trisphosphate. This release was very rapid (less than 0.5 min) and was followed by a slower re-uptake of Ca2+. The microsomal levels of Ca2+ previously attained were not re-established within 5 min. External concentration of free Ca2+ was maintained in the 10(-8)M region during the release. This is the first time that inositol-1,4,5-trisphosphate has been shown to have a regulatory effect on Ca2+ in plant membrane fractions. Phosphoinositides may be important in signal transduction in plant cells, by altering the cytoplasmic Ca2+ activity, a function already known in animal cells.
mesh_terms: D002118:Calcium / Q000378:metabolism*; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000494:pharmacology*; D007700:Kinetics; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism*; D010944:Plants / Q000378:metabolism*; D013403:Sugar Phosphates / Q000494:pharmacology*
chemical_list: D007295:Inositol Phosphates; D013403:Sugar Phosphates; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium