Pharmacology of the Ca2(+)-dependent K+ channel in corn protoplasts.
We investigated the sensitivity of the Ca2(+)-dependent K+ current, IK(Ca), present in corn protoplasts, to different K+ channel blockers. IK(Ca) was inhibited by external Cs+ (10 mM), Ba2+ (10 mM), and quinine (0.5 mM): reagents which block many types of outward-rectifying K+ channels. In contrast 4-aminopyridine (5 mM), an inhibitor of delayed rectifier or inactivating K+ currents, had no effect. Neither of the peptide toxins, apamin or charybdotoxin, specific for Ca2(+)-dependent K+ channels in animal cells, inhibited currents when used in the nanomolar concentration range. However, higher levels of charybdotoxin (10 microM) caused marked reduction of IK(Ca).
Department of Biology, McGill University, Montreal, Quebec, Canada.
K A
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Ketchum
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Poole
D001464:Barium / Q000494:pharmacology; D017609:Barium Compounds; D002118:Calcium / Q000494:pharmacology*; D002586:Cesium / Q000494:pharmacology; D018999:Charybdotoxin; D002712:Chlorides; D008564:Membrane Potentials / Q000187:drug effects; D018521:Plant Physiological Phenomena; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011523:Protoplasts / Q000502:physiology; D011803:Quinine / Q000494:pharmacology; D012604:Scorpion Venoms / Q000494:pharmacology; D003313:Zea mays / Q000502:physiology*
D017609:Barium Compounds; D002712:Chlorides; D015221:Potassium Channels; D012604:Scorpion Venoms; C024986:barium chloride; D018999:Charybdotoxin; D002586:Cesium; D001464:Barium; D011803:Quinine; C028019:cesium chloride; D002118:Calcium