title: GTP mobilization of Ca2+ from the endoplasmic reticulum of islets. Comparison with myo-inositol 1,4,5-trisphosphate.
abstract: The effect of the guanine nucleotide GTP on Ca2+ release from the endoplasmic reticulum of digitonin-permeabilized islets was investigated. maximal and half-maximal Ca2+ release were observed at 5 microM- and 2.5 microM-GTP respectively. GTP caused a rapid release of Ca2+ from the endoplasmic reticulum, which was complete within 1 min. GTP-induced Ca2+ release was structurally specific and required the hydrolysis of GTP. The combination of maximal concentrations of GTP (10 microM) and myo-inositol 1,4,5-trisphosphate (IP3) (10 microM) resulted in an additive effect on Ca2+ release from the endoplasmic reticulum. GDP (100 microM), which inhibits GTP-induced Ca2+ release, did not affect IP3-induced Ca2+ release. Furthermore, GTP-induced Ca2+ release was not independent on submicromolar free Ca2+ concentrations, unlike IP3-induced Ca2+ release. These observations suggest that mechanistically GTP-induced Ca2+ release is different from IP3-induced Ca2+ release from the endoplasmic reticulum.
authors.forename: B A
authors.initials: BA
authors.lastname: Wolf
authors.forename: J
authors.initials: J
authors.lastname: Florholmen
authors.forename: J R
authors.initials: JR
authors.lastname: Colca
authors.forename: M L
authors.initials: ML
authors.lastname: McDaniel
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000494:pharmacology*; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013403:Sugar Phosphates / Q000494:pharmacology*
chemical_list: D007295:Inositol Phosphates; D013403:Sugar Phosphates; D015544:Inositol 1,4,5-Trisphosphate; D006160:Guanosine Triphosphate; D002118:Calcium