alpha 1-Adrenoceptor stimulation partially inhibits ATP-sensitive K+ current in guinea pig ventricular cells: attenuation of the action potential shortening induced by hypoxia and K+ channel openers

Journal of Cardiovascular Pharmacology
T TakizawaHaruaki Nakaya

Abstract

Effects of alpha 1-adrenoceptor stimulation on the action potential shortening produced by K+ channel openers (KCOs) or hypoxia and on the ATP-sensitive K+ current (IK.ATP) activated by KCOs were examined in guinea-pig ventricular cells by using conventional microelectrode and patch-clamp techniques. In papillary muscles, nicorandil (1 mM) or cromakalim (30 microM) markedly shortened the action potential duration (APD) (to 51 +/- 2% and 40 +/- 5% of each control value). Addition of 100 microM methoxamine, an alpha 1-adrenoceptor agonist, partially but significantly reversed the KCOs-induced APD shortening (to 69 +/- 3% and 50 +/- 4% of each control value). The APD-prolonging effect of methoxamine was antagonized by 1 microM prazosin (alpha 1-antagonist) and 100 nM WB4101 (alpha 1A-antagonist) but not by 10 microM chloroethylclonidine (alpha 1B-antagonist). In papillary muscles exposed to a hypoxic, glucose-free solution, APD declined gradually. In the presence of 100 microM methoxamine or 10 microM glibenclamide, the hypoxia-induced action potential shortening was significantly inhibited. In single ventricular myocytes, the KCOs increased a steady-state outward current that was abolished by glibenclamide (1 microM), thereby sug...Continue Reading

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Citations

Dec 12, 2002·Progress in Biophysics and Molecular Biology·Makoto Takano, Shinobu Kuratomi
Oct 24, 1998·Progress in Biophysics and Molecular Biology·E Carmeliet, K Mubagwa
Mar 17, 2001·European Journal of Cardio-thoracic Surgery : Official Journal of the European Association for Cardio-thoracic Surgery·F FarhatM Kirsch
Dec 15, 2015·Physiological Reviews·Monique N Foster, William A Coetzee
Jan 15, 2002·American Journal of Physiology. Heart and Circulatory Physiology·Naoya OketaniChuwa Tei

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