title: Guanosine 5'-triphosphate releases calcium from rat liver and guinea pig parotid gland endoplasmic reticulum independently of inositol 1,4,5-trisphosphate.
abstract: GTP releases calcium from rat liver microsomes and guinea pig parotid gland microsomal subfractions independently of the presence of inositol 1,4,5-trisphosphate (IP3). Non-hydrolyzable guanine nucleotide analogues have no effect and inhibit the effect of GTP. The mechanism of GTP-mediated calcium release differs from IP3-mediated calcium release as indicated by the following findings: GTP-induced calcium release depends on the presence of compounds which increase the viscosity of the medium (polyethylene glycol, polyvinylpyrrolidone, or bovine serum albumin); GTP-mediated calcium release is much slower; GTP-mediated calcium release is strongly temperature-dependent, whereas IP3-mediated calcium release is not; GTP-mediated calcium release is much more sensitive to a decrease of intravesicular free calcium than IP3-mediated calcium release.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002451:Cell Compartmentation; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000494:pharmacology*; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D006168:Guinea Pigs; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000378:metabolism*; D008297:Male; D008861:Microsomes / Q000378:metabolism; D008862:Microsomes, Liver / Q000378:metabolism*; D010306:Parotid Gland / Q000378:metabolism / Q000648:ultrastructure*; D011092:Polyethylene Glycols; D011205:Povidone; D051381:Rats; D011919:Rats, Inbred Strains; D013403:Sugar Phosphates / Q000378:metabolism*; D013696:Temperature; D014783:Viscosity
chemical_list: D007295:Inositol Phosphates; D013403:Sugar Phosphates; D006165:Guanylyl Imidodiphosphate; D011092:Polyethylene Glycols; D015544:Inositol 1,4,5-Trisphosphate; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D011205:Povidone; D002118:Calcium