title: Release of Ca2+ from a non-mitochondrial store site in peritoneal macrophages treated with saponin by inositol 1,4,5-trisphosphate.
abstract: The effects of inositol 1,4,5-trisphosphate, prepared from human erythrocyte ghosts, on Ca2+ release from intracellular store sites were studied in saponin-treated guinea pig peritoneal macrophages. Micromolar concentrations of inositol 1,4,5-trisphosphate released Ca2+ within 1 min from store sites which had accumulated Ca2+ in the presence of 10 mM-NaN3. In the presence of 10 mM-NaN3, the Ca2+ accumulated in the presence of oxalate was seen in the endoplasmic reticulum of saponin-treated macrophages by electron microscopy, indicating that the site of Ca2+ released by inositol 1,4,5-trisphosphate may be endoplasmic reticulum-like membranes. When the concentrations of free Ca2+ were over 3.5 X 10(-6) M, the release of Ca2+ by this agent was inhibited. This inhibition may be due to either the higher concentration of extra-vesicular free Ca2+ or the larger accumulation of Ca2+ into the store site or perhaps both effects. MgCl2 also had an inhibitory effect on the Ca2+ release. Inositol 1,4,5-trisphosphate also released Ca2+ from cardiac sarcoplasmic reticulum, but not from erythrocyte inside-out vesicles.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism; D006168:Guinea Pigs; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D009206:Myocardium / Q000378:metabolism; D012503:Saponins; D013403:Sugar Phosphates / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D007295:Inositol Phosphates; D012503:Saponins; D013403:Sugar Phosphates; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium