Characterization of a charybdotoxin-sensitive intermediate conductance Ca2+-activated K+ channel in porcine coronary endothelium: relevance to EDHF.
1. This study characterizes the K(+) channel(s) underlying charybdotoxin-sensitive hyperpolarization of porcine coronary artery endothelium. 2. Two forms of current-voltage (I/V) relationship were evident in whole-cell patch-clamp recordings of freshly-isolated endothelial cells. In both cell types, iberiotoxin (100 nM) inhibited a current active only at potentials over +50 mV. In the presence of iberiotoxin, charybdotoxin (100 nM) produced a large inhibition in 38% of cells and altered the form of the I/V relationship. In the remaining cells, charybdotoxin also inhibited a current but did not alter the form. 3. Single-channel, outside-out patch recordings revealed a 17.1+/-0.4 pS conductance. Pipette solutions containing 100, 250 and 500 nM free Ca(2+) demonstrated that the open probability was increased by Ca(2+). This channel was blocked by charybdotoxin but not by iberiotoxin or apamin. 4. Hyperpolarizations of intact endothelium elicited by substance P (100 nM; 26.1+/-0.7 mV) were reduced by apamin (100 nM; 17.0+/-1.8 mV) whereas those to 1-ethyl-2-benzimidazolinone (1-EBIO, 600 microM, 21.0+/-0.3 mV) were unaffected (21.7+/-0.8 mV). Substance P, bradykinin (100 nM) and 1-EBIO evoked charybdotoxin-sensitive, iberiotoxin-insensitive whole-cell perforated-patch currents. 5 A porcine homologue of the intermediate-conductance Ca(2+)-activated K(+) channel (IK1) was identified in endothelial cells. 6. In conclusion, porcine coronary artery endothelial cells express an intermediate-conductance Ca(2+)-activated K(+) channel and the IK1 gene product. This channel is opened by activation of the EDHF pathway and likely mediates the charybdotoxin-sensitive component of the EDHF response.
Bychkov
Rostislav
R
Département Diabète et Maladies Métaboliques, Institut de Recherches Servier, 11 rue des Molineaux, 92150 Suresnes, France.
Burnham
Matthew P
MP
Richards
Gillian R
GR
Edwards
Gillian
G
Weston
Arthur H
AH
Félétou
Michel
M
Vanhoutte
Paul M
PM
D000595:Amino Acid Sequence / Q000502:physiology; D000818:Animals; D001685:Biological Factors / Q000502:physiology*; D018999:Charybdotoxin / Q000494:pharmacology*; D003331:Coronary Vessels / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D008969:Molecular Sequence Data; D024681:Potassium Channels, Calcium-Activated / Q000235:genetics / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D013552:Swine
D001685:Biological Factors; D024681:Potassium Channels, Calcium-Activated; C067410:endothelium-dependent hyperpolarization factor; D018999:Charybdotoxin