title: Inositol 1,4,5-trisphosphate releases Ca2+ from a Ca2+-transporting membrane vesicle fraction derived from human platelets.
abstract: Human platelet membrane vesicles that accumulated Ca2+ in the presence of ATP were isolated on an isoosmotic KCl-Percoll gradient. ATP-dependent Ca2+ uptake was stimulated by oxalate and phosphate to steady-state levels of greater than 100 nmol/mg protein, and the accumulated Ca2+ could be largely released by ionophore A23187. Inositol 1,4,5-trisphosphate, in a dose-dependent manner (0.5-5.0 microM), caused the rapid release (less than 5 s) of 40-70% of the total A23187-releasable store of accumulated Ca2+. The membrane vesicles that release accumulated Ca2+ in response to inositol 1,4,5-trisphosphate were enriched in enzymes characteristically found in smooth endoplasmic reticulum. These results support the hypothesis that inositol 1,4,5-trisphosphate, produced by the hydrolysis of phosphatidylinositol 1,4-bisphosphate in response to stimulation of cell surface receptors, is a second messenger mediating the release of Ca2+ from intracellular storage sites.
authors.forename: F A
authors.initials: FA
authors.lastname: O'Rourke
authors.forename: S P
authors.initials: SP
authors.lastname: Halenda
authors.forename: G B
authors.initials: GB
authors.lastname: Zavoico
authors.forename: M B
authors.initials: MB
authors.lastname: Feinstein
mesh_terms: D001792:Blood Platelets / Q000187:drug effects / Q000648:ultrastructure*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000494:pharmacology*; D008566:Membranes / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols / Q000378:metabolism; D013403:Sugar Phosphates / Q000494:pharmacology*
chemical_list: D007295:Inositol Phosphates; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D013403:Sugar Phosphates; D000001:Calcimycin; D015544:Inositol 1,4,5-Trisphosphate; D009251:NADPH-Ferrihemoprotein Reductase; D002118:Calcium