Q- and L-type Ca2+ channels dominate the control of secretion in bovine chromaffin cells

FEBS Lett. 1994 Aug 8;349(3):331-7. doi: 10.1016/0014-5793(94)00696-2.

Abstract

Potassium-stimulated catecholamine release from superfused bovine adrenal chromaffin cells (70 mM K+ in the presence of 2 mM Ca2+ for 10 s, applied at 5-min intervals) was inhibited by the dihydropyridine furnidipine (3 microM) by 50%. omega-Conotoxin MVIIC (CTx-MVIIC, 3 microM) also reduced the secretory response by about half. Combined CTx-MVIIC plus furnidipine blocked 100% catecholamine release. 45Ca2+ uptake and cytosolic Ca2+ concentrations ([Ca2+]i) in K(+)-depolarized cells were partially blocked by furnidipine or CTx-MVIIC, and completely inhibited by both agents. The whole cell current through Ca2+ channels carried by Ba2+ (IBa) was partially blocked by CTx-MVIIC. Although omega-conotoxin GVIA (CTx-GVIA, 1 microM) and omega-agatoxin IVA (Aga-IVA, 0.2 microM) partially inhibited 45Ca2+ entry, IBa and the increase in [Ca2+]i, the combination of both toxins did not affect the K(+)-evoked secretory response. The results are compatible with the presence in bovine chromaffin cells of a Q-like Ca2+ channel which has a prominent role in controlling exocytosis. They also suggest that Q- and L-type Ca2+ channels, but not N- or P-types are localized near exocytotic active sites in the plasmalemma.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenal Medulla / cytology
  • Adrenal Medulla / metabolism*
  • Animals
  • Barium / metabolism
  • Biological Transport
  • Calcium / metabolism
  • Calcium Channel Blockers / pharmacology
  • Calcium Channels / classification
  • Calcium Channels / metabolism*
  • Catecholamines / metabolism*
  • Cattle
  • Cytosol / metabolism
  • Electric Conductivity
  • Models, Biological
  • Neuromuscular Depolarizing Agents / pharmacology
  • Potassium / pharmacology

Substances

  • Calcium Channel Blockers
  • Calcium Channels
  • Catecholamines
  • Neuromuscular Depolarizing Agents
  • Barium
  • Potassium
  • Calcium