The effect of inositol 1,4,5-trisphosphate and GTP on calcium release from rat liver microsomes.
Inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) and GTP mobilized 8% and 90% of the ionophore-releaseable Ca2+ pool from rat liver microsomes, respectively. In contrast to GTP, which acted after a lag-time, the Ins(1,4,5)P3-induced Ca2+ release was immediate. Poly(ethylene glycol) inhibited the effect of Ins(1,4,5)P3 and enhanced that of GTP. Ins(1,4,5)P3 accelerated and enhanced the GTP-induced Ca2+ release. Guanylyl imidodiphosphate inhibited competitively the GTP stimulated Ca2+ release, but not the GTP-dependent phosphorylation of the Mr 17,000 and 38,000 protein bands.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000494:pharmacology*; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000494:pharmacology*; D007700:Kinetics; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism*; D011092:Polyethylene Glycols / Q000494:pharmacology; D051381:Rats; D013403:Sugar Phosphates / Q000494:pharmacology*
D007295:Inositol Phosphates; D013403:Sugar Phosphates; D011092:Polyethylene Glycols; D015544:Inositol 1,4,5-Trisphosphate; D006160:Guanosine Triphosphate; D002118:Calcium