Inhibition by mibefradil, a novel calcium channel antagonist, of Ca2+- and volume-activated Cl- channels in macrovascular endothelial cells

Bernd Nilius, Jean Prenen, Masahiro Kamouchi, Felix Viana, Thomas Voets, Guy Droogmans

Research output: Contribution to journalArticle

106 Citations (Scopus)

Abstract

1. We have studied the effects of mibefradil, a novel calcium antagonist, on the resting potential and ion channel activity of macrovascular endothelial cells (calf pulmonary artery endothelial cells, CPAE). The patch clamp technique was used to measure ionic currents and the Fura-II microfluorescence technique to monitor changes in the intracellular Ca2+ concentration, [Ca2+](i). 2. Mibefradil (10 μM) hyperpolarized the membrane potential of CPAE cells from its mean control value of -26.6 ± 0.6 mV (n = 7) to -59.8 ± 1.7 mV (n = 6). A depolarizing effect was observed at higher concentrations (-13.7 ± 0.6 mV, n = 4, 30 μM mibefradil). 3. Mibefradil inhibited Ca2+-activated Cl- currents, I(Cl),(Ca), activated by loading CPAE cells via the patch pipette with 500 nM free Ca2+ (K(i) = 4.7 ± 0.18 μM, n = 8). 4. Mibefradil also inhibited volume-sensitive Cl- currents, I(Cl),(vol), activated by challenging CPAE cells with a 27% hypotonic solution (K(i) = 5.4 ± 0.22 μM, n = 6). 5. The inwardly rectifying K+ channel, IRK, was not affected by mibefradil at concentrations up to 30 μM. 6. Ca2+ entry activated by store depletion, as assessed by the rate of [Ca2+](i)-increase upon reapplication of 10 mM extracellular Ca2+ to store-depleted cells, was inhibited by 17.6 ± 6.5% (n = 8) in the presence of 10 μM mibefradil. 7. Mibefradil inhibited proliferation of CPAE cells. Half-maximal inhibition was found at 1.7 ± 0.12 μM (n = 3), which is similar to the concentration for half-maximal block of Cl- channels. 8. These actions of mibefradil on Cl- channels and the concomitant changes in resting potential might, in addition to its effect on T-type Ca2+ channels, be an important target for modulation of cardiovascular function under normal and pathological conditions.

Original languageEnglish
Pages (from-to)547-555
Number of pages9
JournalBritish Journal of Pharmacology
Volume121
Issue number3
DOIs
Publication statusPublished - Jun 11 1997
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Pharmacology

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