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).
Ketchum
K A
KA
Department of Biology, McGill University, Montreal, Quebec, Canada.
Poole
R J
RJ
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