title: Cardioprotective effects of stretch are mediated by activation of sarcolemmal, not mitochondrial, ATP-sensitive potassium channels.
abstract: To determine whether sarcolemmal and/or mitochondrial ATP-sensitive potassium (K(ATP)) channels (sarcK(ATP), mitoK(ATP)) are involved in stretch-induced protection, isolated isovolumic rat hearts were assigned to the following protocols: nonstretched hearts were subjected to 20 min of global ischemia (Is) and 30 min of reperfusion, and before Is stretched hearts received 5 min of stretch + 10 min of no intervention. Stretch was induced by a transient increase in left ventricular end-diastolic pressure (LVEDP) from 10 to 40 mmHg. Other hearts received 5-hydroxydecanoate (5-HD; 100 microM), a selective inhibitor of mitoK(ATP), or HMR-1098 (20 microM), a selective inhibitor of sarcK(ATP), before the stretch protocol. Systolic function was assessed through left ventricular developed pressure (LVDP) and maximal rise in velocity of left ventricular pressure (+dP/dt(max)) and diastolic function through maximal decrease in velocity of left ventricular pressure (-dP/dt(max)) and LVEDP. Lactate dehydrogenase (LDH) release and ATP content were also measured. Stretch resulted in a significant increase of postischemic recovery and attenuation of diastolic stiffness. At 30 min of reperfusion LVDP and +dP/dt(max) were 87 +/- 4% and 92 +/- 6% and -dP/dt(max) and LVEDP were 95 +/- 9% and 10 +/- 4 mmHg vs. 57 +/- 6%, 53 +/- 6%, 57 +/- 10%, and 28 +/- 5 mmHg, respectively, in nonstretched hearts. Stretch increased ATP content and did not produce LDH release. 5-HD did not modify and HMR-1098 prevented the protection achieved by stretch. Our results show that the beneficial effects of stretch on postischemic myocardial dysfunction, cellular damage, and energetic state involve the participation of sarcK(ATP) but not mitoK(ATP).
authors.affiliation: Centro de Investigaciones Cardiovasculares, Universidad Nacional de La Plata, 60 y 120, 1900 La Plata, Argentina. smosca@atlas.med.unlp.edu.ar
authors.forename: Susana M
authors.initials: SM
authors.lastname: Mosca
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D048430:Cell Shape; D002470:Cell Survival; D003652:Decanoic Acids / Q000494:pharmacology; D004734:Energy Metabolism; D006880:Hydroxy Acids / Q000494:pharmacology; D066298:In Vitro Techniques; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D008465:Mechanoreceptors / Q000378:metabolism*; D040542:Mechanotransduction, Cellular / Q000187:drug effects; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism*; D009200:Myocardial Contraction; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012508:Sarcolemma / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors; D016277:Ventricular Function, Left; D017725:Ventricular Pressure
chemical_list: D001549:Benzamides; D003652:Decanoic Acids; D006880:Hydroxy Acids; D026902:Potassium Channel Blockers; D015221:Potassium Channels; C117780:mitochondrial K(ATP) channel; C052853:5-hydroxydecanoic acid; D000255:Adenosine Triphosphate; C410297:HMR 1098; D007770:L-Lactate Dehydrogenase