title: Calcium as a coagonist of inositol 1,4,5-trisphosphate-induced calcium release.
abstract: Inositol 1,4,5-trisphosphate (IP3)-induced calcium release from intracellular stores is a regulator of cytosolic-free calcium levels. The subsecond kinetics and regulation of IP3-induced calcium-45 release from synaptosome-derived microsomal vesicles were resolved by rapid superfusion. Extravesicular calcium acted as a coagonist, potentiating the transient IP3-induced release of calcium-45. Thus, rapid elevation of cytosolic calcium levels may trigger IP3-induced calcium release in vivo. Extravesicular calcium also produced a more slowly developing, reversible inhibition of IP3-induced calcium-45 release. Sequential positive and negative feedback regulation by calcium of IP3-induced calcium release may contribute to transients and oscillations of cytosolic-free calcium in vivo.
authors.affiliation: Department of Neurobiology, Harvard Medical School, Boston, MA 02115.
authors.forename: E A
authors.initials: EA
authors.lastname: Finch
authors.forename: T J
authors.initials: TJ
authors.lastname: Turner
authors.forename: S M
authors.initials: SM
authors.lastname: Goldin
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000648:ultrastructure; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002132:Calcium Radioisotopes; D003600:Cytosol / Q000378:metabolism; D004357:Drug Synergism; D006493:Heparin / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D013574:Synaptosomes / Q000648:ultrastructure
chemical_list: D002132:Calcium Radioisotopes; D000001:Calcimycin; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D006493:Heparin; D008274:Magnesium; D002118:Calcium