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Attenuation by phentolamine of hypoxia and levcromakalim‐induced abbreviation of the cardiac action potential
Author(s) -
Tweedie D.,
BoachieAnash G.,
Henderson C.G.,
Kane K.A.
Publication year - 1993
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.1476-5381.1993.tb13945.x
Subject(s) - phentolamine , glibenclamide , chemistry , hypoxia (environmental) , medicine , effective refractory period , endocrinology , electrophysiology , stimulation , diabetes mellitus , organic chemistry , oxygen
1 The effects of phentolamine (5–30 μ m ) and glibenclamide (10 μ m ) on action potential characteristics were examined in guinea‐pig papillary muscle exposed to either hypoxia or levcromakalim (20 μ m ). 2 The hypoxia‐induced abbreviation of action potential duration (APD) and effective refractory period (ERP) were attenuated but not abolished by glibenclamide (10 μ m ). Hypoxia reduced APD by 24 ± 2 vs 65 ± 4% in glibenclamide‐ and vehicle‐treated tissue, respectively. 3 Phentolamine (10–30 μ m ) was less effective than glibenclamide in attenuating the hypoxic shortening of APD since APD was reduced by 38 ± 10, 51 ± 6% vs 65 ± 4% in 10 and 30 μ m phentolamine and vehicle‐treated muscle, respectively. 4 Phentolamine, at concentrations of 10 and 30 μ m , also reduced the upstroke velocity of the action potential and at 5 μ m it increased the APD from 193 ±9 to 221 ± 12 ms. 5 Glibenclamide completely abolished and phentolamine (30 μ m ) significantly attenuated levcromakalim‐induced changes in duration and ERP. Levcromakalim reduced APD by 71 ± 2 and 55 ± 2% in control and phentolamine pretreated muscle, respectively. 6 It is concluded that phentolamine may block K ATP channels at concentrations that also block sodium channels.