The Protective Effects Of Opioid Preconditioning On Rabbit Heart Graft In Hypothermia

Objective To investigate the effects of the selective 5-opioid receptor agonist DADLE(D-Ala2-Leu5-enkephalin) and non-selective opioid receptor agonist morphine preconditioning on rabbit graft in hypothermia.Methods Isogeneic intraabdominal heterotopic heart transplantation was performed on rabbits. The donor rabbits were preconditioned with DADLE(lmg-kg-1) or morphine(lmg-kg-1) or saline respectively(each group n=6),rabbit hearts were excised from donors and stored 4 hours at 4℃ ,then the hearts were transplantated to rabbits. The myocardial functional recovery, left ventricular systolic pressure(LVSP), left ventricular end diastolic pressure(LVeDP), left ventricular development pressure(LVDP) and heart rate(HR) of donor heart were measured every 30 minutes for 2 hours after reperfusion. Serial specimen were performed to assess activity of myocardial Na-K ATPase, contents of the oxygen-derived free radicals(OFRs),levels of the perfiisate LDH,CK and lactic acid effused from coronary vessel and cardial light microscope and ultra structure.Results The recovery of left ventricular functions, the activity of myocardial Na-K ATPase and cardial light microscope and ultra structure in the groups of precondition with DADLE or morphine were better than the control groups(P<0.05). Cardiac enzyme leakage(CK,LDH) was similar among the precondition and the controlgroups(P>0.05). Lactate efflux in the control was more than that in the group of the precondition with opioid during 2 hours after cardial resuscitation (P<0.05). In the groups of precondition with DADLE or morphine increased free radicals production 2-fold versus group C (P<0.001).Conclusion There is a significantly protective role on the exsomatize heart of rabbit with cold storage in the groups of precondition with DADLE and morphine, at least the damage of postischemic reinfusion is availably alleviated in short period. The possible mechanisms :l)It may be the cause of protective role to decrease the lactic acid of perfuate effused from coronary vessel. 2) The resultant increase of free radicals signals may be an important component of the signaling pathways by which DADLE or morphine preconditioning in hearts and it attributed to protecting the structure of the mitochondrion.