Permeation of divalent cations through the Ca2+ channel of rabbit portal vein myocytes

D. A. Katzka, R. Cox, A. J. Davidoff, M. Morad

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

The divalent selectivity of the Ca2+ channel in the rabbit portal vein myocyte was examined by the whole cell clamp method. A concentration- dependent selectivity of divalent ion permeation was found such that when Ca2+ was replaced by Ba2+ or Sr2+, the order of maximum current was Ca2+ = Ba2+ > Sr2+ at 2 mM and Ba2+ > Sr2+ ≥ Ca2+ at 5-10 mM. The possibility of block of the Ca2+ channel by micromolar concentrations of 'contaminant' Ca2+ as a determinant of change in the order of selectivity of divalents was examined. Ethylene glycol-bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid (500 μM) significantly increased maximum Ba2+ current (I(Ba)) or I(Sr) in solution containing 5 mM Ba2+ or Sr2+. Furthermore, at 5 mM extracellular Ba2+ concentration, addition of 10, 20, 50, and 100 μM Ca2+ caused a 6, 14, 22, and 33% decrease in I(Ba), respectively. These results suggest that the portal vein Ca2+ channel has three orders of magnitude higher selectivity for Ca2+ over Ba2+ and Sr2+ such that micromolar Ca2+ may block permeation of other divalents through the channel.

Original languageEnglish (US)
Pages (from-to)H326-H330
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume262
Issue number2 31-2
DOIs
StatePublished - 1992

Keywords

  • anomalous mole fraction
  • patch clamp
  • vascular smooth muscle
  • voltage clamp

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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