Electrophysiological properties of human coronary endothelial cells

Abstract

The electrophysiological properties of human coronary endothelial cells (HCEC) of macro-and microvascular origin were studied using the whole-cell configuration of the patch-clamp technique. The membrane potential of confluent HCEC(−41.9±3.9 mV (mean±SEM, n=32) for macro-and −33.6±22.6 mV (n=64) for microvascular cells, respectively) was less negative than the K⁺ equilibrium potential. Inward currents of isolated cells at potentials below the K⁺ equilibrium potential were blocked by external Ba²⁺ (1 mM), inactivated due to time- and voltage-dependent block caused by external Na⁺, and their amplitudes were enhanced by increasing extracellular [K⁺]; these currents were identified as inwardly rectifying K⁺ currents. Some isolated cells displayed outwardly directed K⁺ currents which were abolished after replacement of Cs⁺ for K⁺ on both sides of the membrane. Voltage-dependent Ca²⁺ currents could not be observed in isolated HCEC. Hyperpolarizations induced by vasoactive agonists have been observed in some endothelial cells from different species. In contrast, extracellularly applied ATP (adenosine-5′-triphosphate) and ADP (adenosine-5′-diphosphate) at micromolar concentrations depolarized confluent HCEC, whereas adenosine had no effect on resting potentials (RP), indicating that the nucleotide-induced depolarizations were mediated via P₂-purinoceptors. These depolarizations occurred even after replacement of N-methyl-D-glucamine for extracellular Na⁺, indicating that Ca²⁺-influx was involved. There were no marked differences in the electrophysiological properties between cells of macro-and microvascular origin.