Electrophysiological properties of human coronary endothelial cells.
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 +/- 2.6 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 Ca(2+)-influx was involved. There were no marked differences in the electrophysiological properties between cells of macro and microvascular origin.
Zünkler
B J
BJ
Federal Institute for Drugs and Medical Devices, Berlin, FRG.
Henning
B
B
Gräfe
M
M
Bass
R
R
Hildebrandt
A G
AG
Fleck
E
E
D000255:Adenosine Triphosphate / Q000378:metabolism*; D003331:Coronary Vessels / Q000378:metabolism* / Q000473:pathology; D004730:Endothelium, Vascular / Q000378:metabolism* / Q000473:pathology; D005110:Extracellular Space / Q000378:metabolism*; D006801:Humans; D008564:Membrane Potentials / Q000502:physiology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*
D000255:Adenosine Triphosphate; D011188:Potassium