Correlation between secretagogue-induced Ca2+ influx, intracellular Ca2+ levels and secretion of catecholamines in cultured adrenal chromaffin cells

Neurochem Int. 1996 Mar;28(3):325-34. doi: 10.1016/0197-0186(96)83614-x.

Abstract

Catecholamine secretion induced by various secretagogues in cultured bovine chromaffin cells has been correlated with Ca2+ influx and intracellular Ca2+ concentrations. Nicotine and high K+ caused prompt secretion of catecholamines from cells. Coincidently, both secretagogues evoked 45[Ca2+] influx with a parallel increase in free intracellular Ca2+ concentration, as determined by Quin 2 fluorescence. However, the rate of return of Ca2+ level to baseline after nicotine stimulation was more rapid than after K+ stimulation. In comparison, stimulation with veratridine produced a slow and prolonged Ca2+ influx accompanied by lower levels of intracellular Ca2+ than those observed after nicotine or K+ stimulation. Yet, during 15 min of stimulation, veratridine induced a substantial catecholamine release, which was larger than that obtained after nicotine or K+ stimulations. The Ca2+ ionophore A23187 (1 microM) induced a pronounced increase in intracellular Ca2+ levels, but did not evoke any significant catecholamine release. Finally, addition of the Ca2+ channel blocker verapamil following stimulation, at a time when intracellular Ca2+ concentration was at its peak level, did not affect the rate of decline in intracellular free Ca2+ concentration but promptly blocked Ca2+ uptake and catecholamine secretion. These findings suggest that the rate of Ca2+ influx, rather than the absolute level of intracellular Ca2+ concentration, determines the rate and extent of catecholamine release.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aminoquinolines
  • Animals
  • Calcimycin / pharmacology
  • Calcium / metabolism*
  • Calcium / physiology
  • Calcium Radioisotopes
  • Catecholamines / metabolism*
  • Cattle
  • Cholinergic Agonists / pharmacology
  • Chromaffin Cells / drug effects
  • Chromaffin Cells / metabolism*
  • Exocytosis / drug effects
  • Exocytosis / physiology
  • Fluorescent Dyes
  • Ionophores / pharmacology
  • Kinetics
  • Nicotine / pharmacology
  • Potassium / pharmacology
  • Stimulation, Chemical
  • Veratridine / pharmacology

Substances

  • Aminoquinolines
  • Calcium Radioisotopes
  • Catecholamines
  • Cholinergic Agonists
  • Fluorescent Dyes
  • Ionophores
  • Calcimycin
  • Nicotine
  • Veratridine
  • Quin2
  • Potassium
  • Calcium