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Characterization of potassium currents modulated by BRL 38227 in rat portal vein
Author(s) -
Noack Thomas,
Deitmer Petra,
Edwards Gillian,
Weston Arthur H.
Publication year - 1992
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1992.tb14400.x
Subject(s) - chemistry , hyperpolarization (physics) , glibenclamide , potassium channel , potassium , current clamp , membrane potential , voltage clamp , cromakalim , patch clamp , reversal potential , biophysics , endocrinology , medicine , biochemistry , stereochemistry , biology , organic chemistry , receptor , nuclear magnetic resonance spectroscopy , diabetes mellitus
1 Smooth muscle cells of the rat portal vein were dispersed by enzymatic treatment and recordings of whole‐cell membrane potassium currents were made by the voltage‐clamp technique. In isolated cells by use of combined voltage‐ and current‐clamp the effect of BRL 38227 on membrane potential and ionic currents was also studied. 2 BRL 38227 (0.1 to 10 μ m ) induced a non‐inactivating potassium current (I KCO ) which developed slowly (900 s to 300 s, respectively) to its full size. These effects of BRL 38227 were reversible. 3 In addition to its K‐channel opening properties, BRL 38227 (1 to 10 μ m ) inhibited the amplitude and changed the activation and inactivation characteristics of a slowly‐inactivating, calcium influx‐independent, outward potassium current ( I TO ). 4 Application of stationary fluctuation analysis to I KCO , showed a mean single channel current of 0.65 pA at −10 mV under a quasi‐physiological potassium gradient. 5 In a combined voltage‐clamp/current‐clamp configuration, BRL 38227 (1 μ m ) induced a mean hyperpolarization of 22 mV. 6 The induction of I KCO by BRL 38227 and the associated hyperpolarization were suppressed by glibenclamide (1 to 10 μ m ) in a concentration‐dependent manner. Glibenclamide (1 μ m ) had no effect on the inhibition of I TO by BRL 38227 (1 μ m ).