Endocannabinoids are implicated in the infarct size-reducing effect conferred by heat stress preconditioning in isolated rat hearts.
OBJECTIVE
We have investigated the involvement of the endocannabinoid system in the delayed cardioprotection conferred by heat stress preconditioning in the isolated rat heart.


METHODS
Rats were divided into eight groups (n=7 in each group), subjected to either heat stress (42 degrees C for 15 min, HS groups) or sham anaesthesia (Sham groups). Twenty-four hours later, their hearts were isolated, retrogradely perfused, and subjected to a 30-min occlusion of the left coronary artery followed by 120 min of reperfusion. Some hearts were perfused with either SR 141716 (a cannabinoid CB(1) receptor antagonist, 1 microM), SR 144528 (a CB(2) receptor antagonist, 1 microM) or L-NAME (a NOS inhibitor, 3 microM) 5 min before ischaemia and during the ischaemic period.


RESULTS
The infarct size-reducing effect conferred by heat stress (35.7+/-1.8% in Sham to 14.1+/-0.6% in HS groups) was not altered by the perfusion of SR 141716 (11.2+/-1.5%) but was abolished by both SR 144528 (36.6+/-1.6%) and L-NAME (32.0+/-4.4%). In hearts from non-heat-stressed rats, perfusion with SR 141716 (32.8+/-1.6%), SR 144528 (33.4+/-2.2%) and L-NAME (31.6+/-2.9%) had no effect on infarct size.


CONCLUSIONS
These results suggest an involvement of endocannabinoids, acting through CB(2) receptors, and NO in the cardioprotection conferred by heat stress against myocardial ischaemia. The possible interaction between both mediators of the heat stress response remains to be determined.
Joyeux
Marie
M
Laboratoire Stress Cardiovasculaires et Pathologies Associées, Faculté de Pharmacie, Domaine de la Merci, 38706 La Tronche, France. marie.joyeux@ujf-grenoble.fr
Arnaud
Claire
C
Godin-Ribuot
Diane
D
Demenge
Pierre
P
Lamontagne
Daniel
D
Ribuot
Christophe
C
D000704:Analysis of Variance; D000818:Animals; D001892:Camphanes / Q000494:pharmacology; D063385:Cannabinoid Receptor Modulators; D002186:Cannabinoids / Q000037:antagonists & inhibitors / Q000378:metabolism*; D063388:Endocannabinoids; D005334:Fever / Q000378:metabolism* / Q000473:pathology; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D008297:Male; D009203:Myocardial Infarction / Q000473:pathology / Q000517:prevention & control*; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010477:Perfusion; D010880:Piperidines / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D043885:Receptor, Cannabinoid, CB2; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000187:drug effects; D000077285:Rimonabant; D013997:Time Factors
D001892:Camphanes; D063385:Cannabinoid Receptor Modulators; D002186:Cannabinoids; C469526:Cnr2 protein, rat; D063388:Endocannabinoids; D010880:Piperidines; D011720:Pyrazoles; D043885:Receptor, Cannabinoid, CB2; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; C110630:SR 144528; D019001:Nitric Oxide Synthase; D000077285:Rimonabant; D019331:NG-Nitroarginine Methyl Ester