Activation of exocytosis by GTP analogues in adrenal chromaffin cells revealed by patch-clamp capacitance measurement

FEBS Lett. 1994 May 16;344(2-3):139-42. doi: 10.1016/0014-5793(94)00361-0.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / pharmacology
  • Adrenal Glands / drug effects
  • Adrenal Glands / physiology*
  • Animals
  • Calcium / pharmacology
  • Cattle
  • Chromaffin System / drug effects
  • Chromaffin System / physiology*
  • Electric Conductivity
  • Exocytosis / drug effects*
  • GTP-Binding Proteins / physiology*
  • Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology
  • Guanosine Diphosphate / analogs & derivatives
  • Guanosine Diphosphate / pharmacology
  • Guanosine Triphosphate / analogs & derivatives*
  • Guanosine Triphosphate / pharmacology
  • Guanylyl Imidodiphosphate / pharmacology
  • Ribonucleotides / pharmacology
  • Thionucleotides / pharmacology


  • Ribonucleotides
  • Thionucleotides
  • Guanosine Diphosphate
  • Guanylyl Imidodiphosphate
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • xanthosine 5'-triphosphate
  • guanosine 5'-O-(2-thiodiphosphate)
  • Guanosine Triphosphate
  • Adenosine Triphosphate
  • GTP-Binding Proteins
  • Calcium