Kinetic analysis of 99mTc-sestamibi evaluates the protective effects by ischaemic preconditioning on ischaemic myocardium in an isolated rabbit heart.
OBJECTIVE
To analyse the kinetic changes of uptake, washout and retention of Tc-sestamibi in order to evaluate the protective effects and possible mechanism of ischaemic preconditioning and adenosine preconditioning on myocardium injured by ischaemia/reperfusion.


METHODS
Isolated ischaemia/reperfusion rabbit heart models, as established by Langendorff, were used. Eighteen rabbit hearts perfused in Krebs-Henseleit (KH) buffer were randomly assigned to three groups: ischaemia/reperfusion (I/R, n=6), adenosine preconditioning (AD, n=6), and ischaemic preconditioning (IPC, n=6). Tc-sestamibi (55.5 MBq) in KH was perfused for 40 min and washed out for 40 min. The kinetic changes of Tc-sestamibi within myocardial tissue was monitored during the uptake and washout phases. Cardiac haemodynamic parameters, creatine kinase and lactate dehydrogenase leakage in coronary effluent, and myocardial infarct size were measured to assess myocardial injuries in rabbit hearts.


RESULTS
In the early phases of uptake, there were no significantly different uptake rates of Tc-sestamibi between AD (before 20 min), IPC (before 15 min) and I/R myocardium (all P>0.05). Uptake rates of Tc-sestamibi in myocardium of the three groups all tended to increase, with the uptake time increasing. In the late phases of uptake, AD and IPC were significantly higher than I/R (all P<0.05). In the washout phases, the retention fractions of Tc-sestamibi in myocardium of the three groups all showed a descending tendency with washout time increasing. The retention fractions in AD and IPC were all higher than I/R (all P<0.05). There were no statistical differences in uptake rates and retention fractions of Tc-sestamibi between AD and IPC (all P>0.05). Cardiac haemodynamic parameters, creatine kinase and lactate dehydrogenase leakage, and myocardial infarct size demonstrated there is lighter injury in AD and IPC myocardium than in I/R (all P<0.05). The retention of Tc-sestamibi and myocardial infarction weight were significantly negatively correlated (r=-0.8384, P<0.001).


CONCLUSIONS
Adenosine preconditioning has similar myocardial protective effects on ischaemia/reperfusion myocardium as does ischaemic preconditioning. Tc-sestamibi may be a sensitive and reliable measure for evaluating the importance and mechanism of ischaemic preconditioning and adenosine preconditioning.
Liang
Jun
J
Department of Nuclear Medicine, Renmin Hospital of WuHan University, WuHan, Hebei, P.R. China. shiyh@public.wh.hb.cn
Chen
Hui-Lin
HL
Zhou
Yi
Y
Xie
Mei
M
Xu
Li-Ming
LM
Lin
Gosheng
G
D000241:Adenosine / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D002317:Cardiovascular Agents / Q000494:pharmacology; D006321:Heart / Q000000981:diagnostic imaging / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D066298:In Vitro Techniques; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D009203:Myocardial Infarction / Q000000981:diagnostic imaging / Q000473:pathology; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging* / Q000517:prevention & control*; D009206:Myocardium / Q000201:enzymology; D049268:Positron-Emission Tomography; D011817:Rabbits; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D015427:Reperfusion Injury / Q000000981:diagnostic imaging / Q000517:prevention & control; D017256:Technetium Tc 99m Sestamibi / Q000493:pharmacokinetics*
D002317:Cardiovascular Agents; D019275:Radiopharmaceuticals; D017256:Technetium Tc 99m Sestamibi; D000241:Adenosine