omega-Agatoxin-IVA-sensitive calcium channels in bovine chromaffin cells

FEBS Lett. 1993 Dec 27;336(2):259-62. doi: 10.1016/0014-5793(93)80815-c.

Abstract

A large component of the whole-cell currents through Ca2+ channels in bovine adrenomedullary chromaffin cells has been shown to be insensitive to both L-type and N-type Ca2+ channel blockers, suggesting the existence of a third type of Ca2+ channel. In the present paper, omega-agatoxin-IVA (AgTx), a selective blocker of P-type Ca2+ channels in mammalian neurons, has been used to investigate the presence of this subtype of Ca2+ channel in bovine chromaffin cells. Barium currents (IBa) through Ca2+ channels were recorded in whole-cell patch-clamped bovine chromaffin cells. IBa was blocked by AgTx in a dose-dependent and irreversible manner. At the maximal concentration used (1 microM), AgTx inhibited IBa by 49.5 +/- 3%. Such a blockade was also present when bovine chromaffin cells were pretreated with 10 microM furnidipine, a novel 1,4-dihydropyridine L-type channel blocker, and after treatment with 1 microM of the N-type channel blocker, omega-conotoxin GVIA (CgTx). A combination of these three types of Ca2+ channel blockers suppressed the macroscopic Ba2+ currents by 88%. We conclude that bovine chromaffin cells, in addition to N- and L-type Ca2+ channels, possess a P-like component in their whole-cell currents through the Ca2+ channels.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenal Medulla / cytology
  • Adrenal Medulla / drug effects*
  • Adrenal Medulla / metabolism
  • Animals
  • Barium / metabolism
  • Binding Sites
  • Calcium Channel Blockers / pharmacology*
  • Cattle
  • Chromaffin System / cytology
  • Chromaffin System / drug effects
  • Chromaffin System / metabolism
  • In Vitro Techniques
  • Ion Channel Gating / drug effects
  • Spider Venoms / pharmacology*
  • omega-Agatoxin IVA

Substances

  • Calcium Channel Blockers
  • Spider Venoms
  • omega-Agatoxin IVA
  • Barium