ArticleBritish journal of pharmacology1993
Attenuation by phentolamine of hypoxia and levcromakalim-induced abbreviation of the cardiac action potential.
Article in British journal of pharmacology, 1993. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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4 authors at 2 institutions in 1 country.
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Abstract
1. The effects of phentolamine (5-30 microM) and glibenclamide (10 microM) on action potential characteristics were examined in guinea-pig papillary muscle exposed to either hypoxia or levcromakalim (20 microM). 2. The hypoxia-induced abbreviation of action potential duration (APD) and effective refractory period (ERP) were attenuated but not abolished by glibenclamide (10 microM). Hypoxia reduced APD by 24 +/- 2 vs 65 +/- 4% in glibenclamide- and vehicle-treated tissue, respectively. 3. Phentolamine (10-30 microM) 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 microM phentolamine and vehicle-treated muscle, respectively. 4. Phentolamine, at concentrations of 10 and 30 microM, also reduced the upstroke velocity of the action potential and at 5 microM it increased the APD from 193 +/- 9 to 221 +/- 12 ms. 5. Glibenclamide completely abolished and phentolamine (30 microM) 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 KATP channels at concentrations that also block sodium channels.
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