Characterization of ion channels in human coronary artery endothelial cells

Abstract

Endothelial ion channels play important roles in regulating coronary vascular tone by modulating endothelial intracellular Ca²⁺ concentration, which in turn controls the production and release of vasoactive substances. These transport molecules either provide direct Ca²⁺ influx pathway through Ca²⁺-permeable non-selective cation channels, or influence Ca²⁺ electrochemical driving force via alterations in the K⁺ and Cl⁻ conductance. We aimed to characterize the type and contribution of ionic currents in human coronary artery endothelial cells (HCAECs), using whole-cell patch clamp technique. Average peak whole-cell current amplitude of HCAECs at +60 mV was 8.07 ± 0.31 pA/pF (n = 336). The percentages of total currents blocked in 10 μM La³⁺, 250 μM DIDS, 1 nM apamin, and 10 μM clotrimazole, were 36.11 ± 1.42% (n = 8), 20.34 ± 2.81% (n = 8), 15.51 ± 1.92% (n = 6), and 19.82 ± 2.02% (n = 10) at +60 mV, suggesting the fractions contributed by non-selective cation, Cl⁻, small-conductance Ca²⁺-sensitive K⁺ (SK_Ca), and intermediate-conductance Ca²⁺-sensitive K⁺ (IK_Ca) channels, respectively (P < 0.05). In addition, 1 mM TEA and 100 nM iberiotoxin could suppress 16.51 ± 5.35% (n = 6) and 16.02 ± 3.99% (n = 5) of the control currents at +60 mV, indicating that the fraction responsible by large-conductance Ca2+-sensitive K⁺ (BK_Ca) channel was about 16%. Thus, HCAEC currents at +60 mV were mostly (> 50%) made up of K⁺ currents, which included, at least, BK_Ca, IK_Ca, and SK_Ca currents. The rest of the currents passed through NSC and Cl⁻ channels. Finally, 100 μM Ba²⁺, a specific blocker of inward rectifier potassium (K_ir) channel, inhibited 37.06 ± 4.59% (n = 6) at -100 mV. These observations could be a basis for further investigation on the role of endothelial ion channels in coronary vascular physiology in human.