Calcium-activated potassium channels in the endothelium of intact rat aorta.
1. Single K+ channel currents and membrane potential were recorded in the endothelium of excised intact rat aorta. 2. Two types of K+ channel were found in excised patches, KCh and KAp. With Na+ and K+ as the main external and internal cations, outward conductances were 6.7 pS (KCh) and 2.8 pS (KAp). In symmetric 150 mM K+, the inward conductances were 18 and 9.1 pS. 3. Activation by Ca2+ was concentration dependent. KCh channels were activated by [Ca2+] > 0.1 microM and KAp by [Ca2+] > 0.5 microM. 4. Apamin at concentrations > 1 nM inhibited KAp Channels. Block was complete at 10 nM. KAp channels were insensitive to charybdotoxin. KCh channels were inhibited by charybdotoxin at concentrations > 50 nM, but were insensitive to apamin. 5. d-Tubocurarine (dTC) evoked flickering activity of KAp channels at concentrations > 5 microM and complete block at 100 microM. At these doses, dTC did not affect KCh channels, but at concentrations > 1 mM it decreased the single channel amplitude. 6. Hyperpolarization evoked by acetylcholine was unaffected by apamin or dTC at low concentrations ( < or = 100 microM), but inhibited by high concentrations of charybdotoxin ( > 50 nM) or dTC ( > 1 mM). 7. These data suggest that KCh channels are novel Ca(2+)-activated K+ channels responsible for the ACh-evoked hyperpolarization in the endothelium of rat aorta.
Marchenko
S M
SM
Physiological Laboratory, University of Cambridge, UK.
Sage
S O
SO
D000109:Acetylcholine / Q000037:antagonists & inhibitors; D000818:Animals; D001011:Aorta / Q000502:physiology*; D001030:Apamin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D018999:Charybdotoxin / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000502:physiology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D014403:Tubocurarine / Q000494:pharmacology
D015221:Potassium Channels; D018999:Charybdotoxin; D001030:Apamin; D000109:Acetylcholine; D002118:Calcium; D014403:Tubocurarine