TY - JOUR
T1 - Sarcolemmal and mitochondrial effects of a KATP opener, P-1075, in "polarized" and "depolarized" Langendorff-perfused rat hearts
AU - Jilkina, Olga
AU - Kuzio, Bozena
AU - Grover, Gary J.
AU - Folmes, Clifford D.L.
AU - Kong, Hee Jeong
AU - Kupriyanov, Valery V.
N1 - Funding Information:
This research was supported, in part, by an operating grant MT 42626 from the Canadian Institutes for Health Research (CIHR) to V.V. Kupriyanov.
PY - 2003/12/3
Y1 - 2003/12/3
N2 - We investigated consequences of cardiac arrest on sarcolemmal and mitochondrial effects of ATP-sensitive potassium channel (KATP) opener, P-1075, in Langendorff-perfused rat hearts. Depolarised cardiac arrest (24.7 mM KCl) did not affect glibenclamide-sensitive twofold activation of rubidium efflux by P-1075 (5 μM) from rubidium-loaded hearts, but eliminated uncoupling produced by P-1075 in beating hearts: 40% depletion of phosphocreatine and ATP, 50% increase in oxygen consumption, and reduction of cytochrome c oxidase. Depolarized cardiac arrest by calcium channel blocker, verapamil (5 μM), also prevented uncoupling. Lack of P-1075 mitochondrial effects in depolarized hearts was not due to changes in phosphorylation potential, because 2,4-dintrophenol (10 μM) reversed the [PCr]/[Cr] increase and Pi decrease, characteristic of KCl-arrest, but did not restore uncoupling. In agreement with this conclusion, pyruvate (5 mM) increased [PCr]/[Cr] and decreased Pi, but did not prevent uncoupling in beating hearts. A decrease in mean [Ca2+] in KCl-arrested hearts could not account for lack of P-1075 mitochondrial effects, because calcium channel opener, S-(-)-Bay K8644 (50 nM), and beta-agonist, isoproterenol (0.5 μM), did not facilitate uncoupling. In contrast, in adenosine (1 mM) -arrested hearts (polarized arrest), P-1075 caused 40% phosphocreatine and ATP depletion. In isolated rat liver mitochondria, P-1075 (20 μM) decreased mitochondrial membrane potential (ΔΨ) by approximately 14 mV (demonstrated by redistribution of ΔΨ-sensitive dye, rhodamine 800) in a glibenclamide-sensitive manner. We concluded that cell membrane depolarization does not prevent activation of sarcolemmal KATP by P-1075, but it plays a role in mitochondrial uncoupling effects of P-1075.
AB - We investigated consequences of cardiac arrest on sarcolemmal and mitochondrial effects of ATP-sensitive potassium channel (KATP) opener, P-1075, in Langendorff-perfused rat hearts. Depolarised cardiac arrest (24.7 mM KCl) did not affect glibenclamide-sensitive twofold activation of rubidium efflux by P-1075 (5 μM) from rubidium-loaded hearts, but eliminated uncoupling produced by P-1075 in beating hearts: 40% depletion of phosphocreatine and ATP, 50% increase in oxygen consumption, and reduction of cytochrome c oxidase. Depolarized cardiac arrest by calcium channel blocker, verapamil (5 μM), also prevented uncoupling. Lack of P-1075 mitochondrial effects in depolarized hearts was not due to changes in phosphorylation potential, because 2,4-dintrophenol (10 μM) reversed the [PCr]/[Cr] increase and Pi decrease, characteristic of KCl-arrest, but did not restore uncoupling. In agreement with this conclusion, pyruvate (5 mM) increased [PCr]/[Cr] and decreased Pi, but did not prevent uncoupling in beating hearts. A decrease in mean [Ca2+] in KCl-arrested hearts could not account for lack of P-1075 mitochondrial effects, because calcium channel opener, S-(-)-Bay K8644 (50 nM), and beta-agonist, isoproterenol (0.5 μM), did not facilitate uncoupling. In contrast, in adenosine (1 mM) -arrested hearts (polarized arrest), P-1075 caused 40% phosphocreatine and ATP depletion. In isolated rat liver mitochondria, P-1075 (20 μM) decreased mitochondrial membrane potential (ΔΨ) by approximately 14 mV (demonstrated by redistribution of ΔΨ-sensitive dye, rhodamine 800) in a glibenclamide-sensitive manner. We concluded that cell membrane depolarization does not prevent activation of sarcolemmal KATP by P-1075, but it plays a role in mitochondrial uncoupling effects of P-1075.
KW - ATP-sensitive potassium channel
KW - Cytochrome c oxidase
KW - K opener
KW - Oxidative phosphorylation
KW - Oxygen consumption
KW - P-1075
KW - Rb/K efflux
KW - Sarcolemmal polarization
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U2 - 10.1016/j.bbamem.2003.10.004
DO - 10.1016/j.bbamem.2003.10.004
M3 - Article
C2 - 14643932
AN - SCOPUS:0345276641
SN - 0005-2736
VL - 1618
SP - 39
EP - 50
JO - Biochimica et Biophysica Acta - Biomembranes
JF - Biochimica et Biophysica Acta - Biomembranes
IS - 1
ER -