ELECTROPHYSIOLOGICAL PROPERTIES OF HUMAN CORONARY ENDOTHELIAL-CELLS

The electrophysiological properties of human coronary endothelial cell s (HCEC) of macro- and microvascular origin were studied using the who le-cell configuration of the patch-clamp technique. The membrane poten tial of confluent HCEC (-41.9 +/- 3.9 mV (mean +/- SEM, n = 32) for ma cro- and -33.6 +/- 2.6 mV (n = 64) for microvascular cells, respective ly) was less negative than the K+ equilibrium potential. Inward curren ts of isolated cells at potentials below the K+ equilibrium potential were blocked by external Ba2+ (1 mM), inactivated due to time- and vol tage-dependent block caused by external Na+, and their amplitudes were enhanced by increasing extracellular K+; these currents were identi fied 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+ c urrents could not be observed in isolated HCEC. Hyperpolarizations ind uced by vasoactive agonists have been observed in some endothelial cel ls from different species. In contrast, extracellularly applied ATP (a denosine-5'-triphosphate) and ADP (adenosine-5'-diphosphate) at microm olar concentrations depolarized confluent HCEC, whereas adenosine had no effect on resting potentials (RP), indicating that the nucleotide-i nduced depolarizations were mediated via P-2-purinoceptors. These depo larizations occurred even after replacement of N-methyl-D-glucamine fo r extracellular Na+, indicating that Ca2+-influx was involved. There w ere no marked differences in the electrophysiological properties betwe en cells of macro- and microvascular origin.