Potassium single-channel properties in normal and Rous sarcoma virus-transformed chicken embryo fibroblasts.
Ion channels in normal and Rous sarcoma virus (RSV)-transformed chicken embryo fibroblasts (CEFs) were examined by using the patch-clamp technique. Three different types of ion channels were observed with single-channel conductances in symmetrical 140 mM KCl (with frequencies of occurrence in parentheses) of 186 pS (70%), 110 pS (10%), and 65 pS (20%), which are identical in normal and RSV-transformed CEFs. The total channel density in both cell types is about 0.13 per micron2. All three types of channels are highly selective for K+ ions, they are Ca(2+)- and voltage-dependent, and they can be completely blocked by external tetraethylammonium (10 mM) in both normal and RSV-transformed cells. Some channel properties, however, are different in normal and RSV-transformed CEFs. The K186 channel of normal CEFs is almost completely activated in the presence of about 1 nM free internal Ca2+ and is insensitive to charybdotoxin (100 nM). In contrast, the K186 channel of RSV-transformed CEFs has an EC50 value for activation by internal Ca2+ of about 100 nM and is highly sensitive to charybdotoxin (IC50 = 9 nM). In normal CEFs, the K186 channel activity starts at membrane potentials more positive than -50 mV and reaches a high open state probability of 0.94 at +50 mV. In RSV-transformed CEFs, the threshold of K186 channel activity is also -50 mV but the maximal open state probability is only 0.70 at +50 mV membrane potential. Averages of current traces of K186 channels show the typical features of the macroscopic K+ currents described previously for normal and RSV-transformed CEFs.(ABSTRACT TRUNCATED AT 250 WORDS)
Draheim
H
H
Rudolf-Buchheim-Institut für Pharmakologie der Justus-Liebig-Universität Giessen, Germany.
Repp
H
H
Malettke
N
N
Dreyer
F
F
D000818:Animals; D001358:Avian Sarcoma Viruses / Q000502:physiology*; D002118:Calcium / Q000494:pharmacology; D002461:Cell Line, Transformed / Q000378:metabolism; D002472:Cell Transformation, Viral; D018999:Charybdotoxin; D002642:Chick Embryo / Q000166:cytology* / Q000378:metabolism*; D004594:Electrophysiology; D005347:Fibroblasts / Q000378:metabolism; D011188:Potassium / Q000493:pharmacokinetics; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000145:classification / Q000502:physiology*; D012016:Reference Values; D012604:Scorpion Venoms / Q000494:pharmacology
D026902:Potassium Channel Blockers; D015221:Potassium Channels; D012604:Scorpion Venoms; D018999:Charybdotoxin; D011188:Potassium; D002118:Calcium