title: Direct stimulation by thyrotropin-releasing hormone (TRH) of polyphosphoinositide hydrolysis in GH3 cell membranes by a guanine nucleotide-modulated mechanism.
abstract: Polyphosphoinositide hydrolysis was examined in membranes from thyrotropin-releasing hormone (TRH)-responsive GH3 pituitary cells. [3H]Inositol phosphates (IP2 and IP3) were generated upon incubation of membranes from [3H]inositol-labeled cells indicating the presence of a membrane-associated polyphosphoinositide phosphodiesterase (PPI PDE). Membrane PPI PDE activity was found to be stimulated by TRH and by GTP-gamma-S in Ca2+-modulated manner. In addition, TRH-stimulated PPI hydrolysis was potentiated by GTP. These results demonstrate direct in vitro effects of a hormone on PPI turnover and suggest the involvement of a GTP-binding component in transmembrane signalling by TRH.
mesh_terms: D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000494:pharmacology*; D006868:Hydrolysis; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols / Q000378:metabolism*; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D013268:Stimulation, Chemical; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*
chemical_list: D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D013973:Thyrotropin-Releasing Hormone; D006160:Guanosine Triphosphate