Voltage-dependent K(+) current in capillary endothelial cells isolated from guinea pig heart.
Capillary fragments were isolated from guinea pig hearts, and their electrical properties were studied using the perforated-patch and cell-attached mode of the patch-clamp technique. A voltage-dependent K(+) current was discovered that was activated at potentials positive to -20 mV and showed a sigmoid rising phase. For depolarizing voltage steps from -128 to +52 mV, the time to peak was 71 +/- 5 ms (mean +/- SE) and the amplitude of the current was 3.7 +/- 0.5 pA/pF in the presence of 5 mM external K(+). The time course of inactivation was exponential with a time constant of 7.2 +/- 0.5 s at +52 mV. The current was blocked by tetraethylammonium (inhibitory constant approximately 3 mM) but was not affected by charybdotoxin (1 microM) or apamin (1 microM). In the cell-attached mode, depolarization-activated single-channel currents were found that inactivated completely within 30 s; the single-channel conductance was 12.3 +/- 2.4 pS. The depolarization-activated K(+) current described here may play a role in membrane potential oscillations of the endothelium.
Institut für Normale und Pathologische Physiologie, Universität Marburg, D-35037 Marburg, Germany. michael.dittrich@uni-koeln.de
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D000200:Action Potentials; D000818:Animals; D004594:Electrophysiology; D004730:Endothelium, Vascular / Q000166:cytology* / Q000502:physiology*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D009206:Myocardium / Q000166:cytology*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000502:physiology*; D026902:Potassium Channel Blockers
D026902:Potassium Channel Blockers; D011188:Potassium