title: Opioid-induced second window of cardioprotection: potential role of mitochondrial KATP channels.
abstract: Opioids have been previously shown to confer short-term cardioprotection against a prolonged ischemic insult. Therefore, the present study was designed to determine whether opioids can induce a delayed or "second window" of cardioprotection and to assess the potential involvement of the mitochondrial KATP channel. All rats were subjected to 30 minutes of ischemia and 2 hours of reperfusion (I/R). Control animals, injected with saline 24 hours before I/R, elicited an infarct size/area at risk (IS/AAR) of 62.9+/-3.4. TAN-67, a delta1-opioid receptor agonist, was administered 10 or 30 mg/kg IP 12, 24, 48, or 72 hours before I/R. TAN-67 (10 mg/kg) 12- or 24-hour pretreatment did not significantly reduce IS/AAR (62.1+/-6.3 and 43.3+/-7.3, respectively). Similarly, 12-hour pretreatment with TAN-67 (30 mg/kg) did not reduce IS/AAR (60.0+/-5.6); however, 24-hour pretreatment significantly reduced IS/AAR (34.5+/-5.9). Forty-eight-hour pretreatment with TAN-67 maximally reduced IS/AAR (29.2+/-7.0), and opioid-induced cardioprotection was lost after 72-hour pretreatment (61.7+/-3.8). TAN-67-induced cardioprotection could be abolished by pretreatment with the selective delta1-opioid receptor antagonist 7-benzylidenenaltrexone, BNTX, administered either 30 minutes before TAN-67 given 48 hours before I/R or 10 minutes before I/R in rats previously treated for 48 hours with TAN-67 (59.6+/-3.1 and 58.7+/-3.5, respectively). The involvement of the KATP channel was investigated with 2 inhibitors: glibenclamide, a nonselective KATP channel inhibitor, and 5-hydroxydecanoic acid, selective for the mitochondrial KATP channel in rabbits. Glibenclamide, administered 30 minutes before I/R in 48-hour TAN-67-pretreated rats, completely abolished cardioprotection (60. 4+/-3.2). Similarly, 5-hydroxydecanoic acid, administered 5 minutes before I/R in rats pretreated 48 hours previously with TAN-67, completely abolished cardioprotection (57.8+/-2.5). These results suggest that delta1-opioid receptor stimulation, 24 to 48 hours before an ischemic insult, produces a delayed cardioprotective effect that is possibly the result of mitochondrial KATP channel activation.
authors: Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA.
authors: R M
authors: RM
authors: Fryer
authors: A K
authors: AK
authors: Hsu
authors: J T
authors: JT
authors: Eells
authors: H
authors: H
authors: Nagase
authors: G J
authors: GJ
authors: Gross
mesh_terms: D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D001597:Benzylidene Compounds / Q000494:pharmacology; D001794:Blood Pressure; D003326:Coronary Circulation; D005905:Glyburide / Q000494:pharmacology; D007004:Hypoglycemic Agents / Q000494:pharmacology; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D008928:Mitochondria / Q000737:chemistry*; D009203:Myocardial Infarction / Q000188:drug therapy / Q000503:physiopathology; D017202:Myocardial Ischemia / Q000188:drug therapy / Q000503:physiopathology*; D015428:Myocardial Reperfusion Injury / Q000188:drug therapy / Q000503:physiopathology*; D009206:Myocardium / Q000737:chemistry; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology*; D011804:Quinolines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017465:Receptors, Opioid, delta / Q000502:physiology*
chemical_list: D000700:Analgesics; D001597:Benzylidene Compounds; D007004:Hypoglycemic Agents; D009292:Narcotic Antagonists; D015221:Potassium Channels; D011804:Quinolines; D017465:Receptors, Opioid, delta; C094142:TAN 67; C077358:7-benzylidenenaltrexone; D009271:Naltrexone; D005905:Glyburide