Ion channels in rabbit cultured fibroblasts.
Large outward currents are recorded with the whole-cell patch-clamp technique on depolarization of rabbit cultured fibroblasts. Our findings suggest that these outward currents consist of two voltage-dependent components, one of which also depends on cytoplasmic calcium concentration. Total replacement of external Cl- by the large anion ascorbate does not affect the amplitude of the currents, indicating that both components must be carried by K+. Consistent with these findings with whole-cell currents, in single channel recordings from fibroblasts we found that most patches contain high-conductance potassium-selective channels whose activation depends on both membrane potential and the calcium concentration at the cytoplasmic surface of the membrane. In a smaller number of patches, a second population of high-conductance calcium-independent potassium channels is observed having different voltage-dependence. The calcium- and voltage-dependence suggest that these two channels correspond with the two components of outward current seen in the whole-cell recordings. The single channel conductance of both channels in symmetrical KCl (150 mM) is 260-270 pS. Both channels are highly selective for K+ over both Na+ and Cl-. The conductance of the channels when outward current is carried by Rb+ is considerably smaller than when it is carried by K+. Some evidence is adduced to support the hypothesis that these potassium channel populations may be involved in the control of cell proliferation.
Gray
P T
PT
Chiu
S Y
SY
Bevan
S
S
Ritchie
J M
JM
D015761:4-Aminopyridine; D000631:Aminopyridines / Q000494:pharmacology; D029845:Amphibian Proteins; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000032:analysis; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D011188:Potassium / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D012530:Saxitoxin / Q000494:pharmacology; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
D000631:Aminopyridines; D029845:Amphibian Proteins; D002352:Carrier Proteins; D002712:Chlorides; D007473:Ion Channels; D013757:Tetraethylammonium Compounds; C027525:saxitoxin-binding protein, Rana catesbeiana; D012530:Saxitoxin; D013779:Tetrodotoxin; D015761:4-Aminopyridine; D011188:Potassium; D002118:Calcium