Fast exocytosis and endocytosis triggered by depolarisation in single adrenal chromaffin cells before rapid Ca2+ current run-down

Pflugers Arch. 1995 Jun;430(2):213-9. doi: 10.1007/BF00374652.

Abstract

The kinetics of exocytosis and membrane retrieval (endocytosis) were examined in bovine chromaffin cells using membrane capacitance measurement during whole-cell recording. At early times after breakthrough to the whole-cell recording mode, depolarisation for 1 s resulted in a fast (600 vesicles per s) exocytotic response and efficient membrane retrieval with a time constant of 25 s. The ability to activate fast exocytosis and retrieval was lost during intracellular dialysis, with a time constant of 40 s. At later times, a slow exocytotic response could be elicited with no membrane retrieval following single depolarisations. The wash-out of the responses appeared to be due to a rapid loss of a portion of the Ca2+ current. Trains of depolarisation at late times after breakthrough could elicit a fast (time constant 4 s) retrieval. These data show that in addition to a previously studied slow Ca(2+)-independent retrieval mechanism, chromaffin cells also possess an efficient and rapid retrieval pathway coupled to exocytosis that can be activated following depolarisation. The fast endocytosis appears to have a higher threshold for activation than exocytosis, probably due to a higher Ca2+ requirement. Rapid membrane retrieval appears to occur via a clathrin-independent pathway in chromaffin cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 8-Bromo Cyclic Adenosine Monophosphate / pharmacology
  • Action Potentials
  • Adrenal Medulla / physiology*
  • Animals
  • Calcium / pharmacology
  • Calcium Channels / physiology*
  • Cattle
  • Chromaffin System / physiology*
  • Cyclic AMP / pharmacology
  • Dialysis
  • Egtazic Acid / pharmacology
  • Electric Conductivity
  • Endocytosis*
  • Ethylmaleimide / pharmacology
  • Exocytosis*
  • Membrane Potentials

Substances

  • Calcium Channels
  • 8-Bromo Cyclic Adenosine Monophosphate
  • Egtazic Acid
  • Cyclic AMP
  • Ethylmaleimide
  • Calcium