title: Activation of exocytosis by GTP analogues in adrenal chromaffin cells revealed by patch-clamp capacitance measurement.
abstract: The role of GTP-binding proteins in exocytosis in bovine adrenal chromaffin cells was examined using patch-clamp capacitance measurement. Internal dialysis with the non-hydrolysable GTP analogue guanosine 5'-[beta gamma-imido]triphosphate and xanthosine triphosphate (XTP) activated a capacitance increase. Exocytosis triggered by XTP was blocked by guanosine 5'-[beta-thio]diphosphate (GDP beta S) but Ca(2+)-induced exocytosis was unaffected. The capacitance increase due to XTP could not be explained by Ca2+ mobilisation since Ins(1,4,5)P3 and caffeine did not mimic the response. Chromaffin cells appear to possess a Ca(2+)-independent pathway for exocytosis that involves GTP-binding proteins. The magnitude of the response to XTP suggested that GTP analogues stimulate both exocytosis and recruitment of secretory granules.
authors.affiliation: Physiological Laboratory, Liverpool, UK.
authors.forename: R D
authors.initials: RD
authors.lastname: Burgoyne
authors.forename: S E
authors.initials: SE
authors.lastname: Handel
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000311:Adrenal Glands / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D002838:Chromaffin System / Q000187:drug effects / Q000502:physiology*; D004553:Electric Conductivity; D005089:Exocytosis / Q000187:drug effects*; D019204:GTP-Binding Proteins / Q000502:physiology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D012265:Ribonucleotides / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology
chemical_list: D012265:Ribonucleotides; D013873:Thionucleotides; D006153:Guanosine Diphosphate; D006165:Guanylyl Imidodiphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C065326:xanthosine 5'-triphosphate; C023427:guanosine 5'-O-(2-thiodiphosphate); D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D019204:GTP-Binding Proteins; D002118:Calcium