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Delta opioid receptor stimulation mimics ischemic preconditioning in human heart muscle

Sam P. Bell, BSc, MBBS^*, Michael N. Sack, PhD, MBBCh, Asha Patel, HND^*, Lionel H. Opie, MD, DPhil, FRCP and Derek M. Yellon, DSc, MRCP, FESC, FACC^*

^* The Hatter Institute, University College London Hospitals and Medical School, London, United Kingdom
The Hatter Institute, Cape Heart Center, University of Cape Town, Cape Town, South Africa

View larger version (42K): [in a new window]   Figure 1 Experimental protocols for eight experimental groups. All protocols were preceded by a stabilization period of 45 to 60 min. This was followed by 90 min of simulated ischemia (superfusion with hypoxic, substrate free Modified Tyrodes solution and pacing at 3 Hz) and 120 min of superfusion with reoxygenated Tyrodes solution. Control = C; preconditioning = PC; delta opioid agonist = DADLE; naltrindole + preconditioning = naltrindole + PC; 5-hydroxydecanoate = 5HD. Solid box = simulated ischemia; open box = normoxic superfusion.

View larger version (29K): [in a new window]   Figure 2 (A) Representative RT-PCR reactions at 35 cycles (Cyc) and 40 cycles, respectively. The control primers (GAPDH ([G]) have multiple bands due to the different optimal annealing temperatures of the GAPDH primers compared with the opioid-receptor subtypes. The µ and receptor PCR products are shown at the different cycle lengths. The receptor nested PCR data are not shown. (B) This histogram demonstrates the relative intensities (expressed in arbitrary units [AU]) of the PCR products of the opioid receptor subtypes in both human atrial and ventricular tissue. The AU for the µ and receptor subtypes reflect the mean PCR product generated after 40 cycles of PCR, and the AU for the receptor reflects the PCR products after the second round of nested PCR. bp = base pair; MRNA = messenger RNA; PCR = polymerase chain reaction.

View larger version (26K): [in a new window]   Figure 3 Developed force presented as a percentage of baseline developed force against time. This graph shows that the effect of PC with hypoxia may be simulated by delta-opioid receptor agonism (DADLE) and that ischemic PC is blocked by the delta opioid receptor antagonist, naltrindole. p < 0.001 vs. control. C = control; DADLE = opioid agonist; PC = preconditioning; naltrindole+PC = naltrindole plus preconditioning.

View larger version (27K): [in a new window]   Figure 4 Developed force presented as a percentage of baseline developed force against time. This graph shows that the effect of PC with both simulated ischemia and DADLE. Both the effects of PC and DADLE are blocked by the mitochondrial KATP channel blocker 5HD. p < 0.001 vs. control. C = control; PC = preconditioning; DADLE = delta opioid agonist; 5HD = 5-hydroxydecanoate; 5HD+PC = 5 hydroxyceanoate plus preconditioning; 5HD+DADLE = 5 hydroxydecanoate plus delta opioid agonist.