ISSN:
1432-1424
Schlagwort(e):
Potassium channels
;
Whole-cell recording
;
BRL 38227
;
Pulmonary artery
;
KATP channels
;
Noise analysis
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
,
Chemie und Pharmazie
Notizen:
Abstract Tension and patch clamp recording techniques were used to investigate the relaxation of rabbit pulmonary artery and the properties of the K+ current activated by levcromakalim in isolated myocytes. Under whole-cell voltage clamp, holding at −60 mV in symmetrical 139 mm K+, levcromakalim (10 μm) induced a noisy inward current of −116 ± 19 pA (n = 13) which developed over 1 to 2 min. This current could be blocked by either glibenclamide (10 μm) or phencyclidine (5–50 μM) and was unaffected when extracellular Ca2+ was removed. Both these drugs inhibited the levcromakalim-induced relaxation of muscle strips precontracted with 20 mm [K+] o . Application of voltage ramps in symmetrical 139 mm K+ confirmed that the levcromakalim-induced current was carried by K+ ions and was weakly voltage dependent over the potential range from −100 to +40 mV. The unitary current amplitude and density of the channels underlying the levcromakalim-activated whole-cell K+ current was estimated from the noise in the current record. We estimate that levcromakalim caused activation of around 300 channels per cell, with a single channel current of 1.1 pA, corresponding to a slope conductance of about 19 pS. Furthermore, cells dialyzed with an ATP-free pipette solution developed a large noisy inward current at −60 mV, which could subsequently be blocked by flash photolysis of caged ATP. Analysis of the noise associated with this current indicated that the single channel amplitude underlying the ATP-blocked current was 1.4 pA, a value similar to that estimated for the levcromakalim-induced current. We conclude that the conductance of this ATP-sensitive channel is likely to be small under physiological conditions and that it is present at low density.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00233709
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