title: Ischaemic and morphine-induced post-conditioning: impact of mK(Ca) channels.
abstract: BACKGROUND
  Mitochondrial calcium-sensitive potassium (mK(Ca)) channels are involved in cardiac preconditioning. In the present study, we investigated whether also ischaemic-, morphine-induced post-conditioning, or both is mediated by the activation of mK(Ca) channels in the rat heart in vitro.
  
  
  METHODS
  Animals were treated in compliance with institutional and national guidelines. Male Wistar rats were randomly assigned to one of seven groups (each n = 7). Control animals were not further treated. Post-conditioning was induced either by 3 × 30 s of ischaemia/reperfusion (I-PostC) or by administration of morphine (M-PostC, 1 µM) for 15 min at the onset of reperfusion. The mK(Ca)-channel inhibitor paxilline (1 µM) was given with and without post-conditioning interventions (M-PostC+Pax, I-PostC+Pax, and Pax). As a positive control, we determined whether direct activation of mK(Ca) channels with NS1619 (10 µM) induced cardiac post-conditioning (NS1619). Isolated hearts underwent 35 min ischaemia followed by 120 min reperfusion. At the end of reperfusion, infarct sizes were measured by triphenyltetrazolium chloride staining.
  
  
  RESULTS
  In the control group, infarct size was 53 (5)% of the area at risk. Morphine- and ischaemic post-conditioning reduced infarct size in the same range [M-PostC: 37 (4)%, I-PostC: 35 (5)%; each P<0.05 vs control]. The mK(Ca)-channel inhibitor paxilline completely blocked post-conditioning [M-PostC+Pax: 47 (7)%, I-PostC+Pax: 51 (3)%; each P<0.05 vs M-PostC and I-PostC, respectively]. Paxilline itself had no effect on infarct size (NS vs control). NS1619 reduced infarct size to 33 (4)% (P < 0.05 vs control).
  
  
  CONCLUSIONS
  Ischaemic- and morphine-induced post-conditioning is mediated by the activation of mK(Ca) channels.
authors.affiliation: Department of Anaesthesiology, University Hospital Duesseldorf, University Hospital Duesseldorf.
authors.forename: R
authors.initials: R
authors.lastname: Huhn
authors.forename: A
authors.initials: A
authors.lastname: Heinen
authors.forename: N C
authors.initials: NC
authors.lastname: Weber
authors.forename: W
authors.initials: W
authors.lastname: Schlack
authors.forename: B
authors.initials: B
authors.lastname: Preckel
authors.forename: M W
authors.initials: MW
authors.lastname: Hollmann
mesh_terms: D000818:Animals; D001835:Body Weight; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D008297:Male; D008929:Mitochondria, Heart / Q000378:metabolism; D009020:Morphine / Q000627:therapeutic use*; D009203:Myocardial Infarction / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D009206:Myocardium / Q000473:pathology; D009924:Organ Culture Techniques; D009929:Organ Size; D024681:Potassium Channels, Calcium-Activated / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D024681:Potassium Channels, Calcium-Activated; D009020:Morphine