Ca-activated K channel in cultured smooth muscle cells of rat aortic media.
Electrical and pharmacological properties of the single Ca-activated K channel in cultured smooth muscle cells (SMC) of the rat aorta were studied with the patch-clamp technique. The Ca-activated K channel had a slope conductance (gamma K) of 135 +/- 2 pS (mean +/- SE; n = 5) in symmetrical 142 mM K solutions. The reversal potentials show a 56-mV change for a 10-fold change in the external K concentration. Probability of the channel opening increased when the intracellular Ca concentration ([Ca]i) was increased over 10(-7) M or the membrane was depolarized. The channel was blocked by either external tetraethylammonium (TEA, 10-30 mM) or by internal Ba (1-5 mM). Channel activities were characterized by burst-like openings. Open-time histogram was fitted with a single exponential (tau = 1.3 ms at +10 mV and 10(-7) M [Ca]i), whereas the closed-time histogram was fitted with two exponentials (tau 1 = 0.7 ms and tau 2 = 111 ms). The permeability ratio for monovalent cations calculated with the Goldman-Hodgkin-Katz equation was K:Rb:Na = 1:0.7: less than 0.01. We conclude from these observations that the Ca-activated K channel in cultured SMC of the rat aorta is characterized by a middle size gamma K, activation by [Ca]i increase and depolarization, relatively low sensitivity to TEA, and high selectivity for K ions.
Sadoshima
J
J
Research Institute of Angiocardiology and Cardiovascular Clinic, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Akaike
N
N
Tomoike
H
H
Kanaide
H
H
Nakamura
M
M
D000818:Animals; D001011:Aorta / Q000502:physiology*; D002118:Calcium / Q000494:pharmacology*; D004553:Electric Conductivity; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008962:Models, Theoretical; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D007473:Ion Channels; D011188:Potassium; D002118:Calcium