Detection of cardiomyocyte death in a rat model of ischemia and reperfusion using 99mTc-labeled annexin V.
There is increasing evidence that cell death after myocardial ischemia and reperfusion may begin as apoptosis rather than necrosis. To determine the time course, location, and extent of this process, we studied groups of rats after a 20-min interval of coronary occlusion and reperfusion.


METHODS
After thoracotomy, the left coronary artery was occluded for 20 min. After release and before study, groups of animals were allowed to recover for various intervals: 0.5 h (n = 6), 1.5 h (n = 7), 6 h (n = 7), 1 d (n = 8), 3 d (n = 8), or 2 wk (n = 5). At the time of study, the rats were injected with 99mTc-annexin V (80-150 MBq). One hour later, to verify the area at risk, 201Tl (0.74 MBq) was injected intravenously just after the left coronary artery reocclusion and the rats were sacrificed 1 min later. Dual-tracer autoradiography was performed to assess 99mTc-annexin V uptake and the area at risk.


RESULTS
Extensive 99mTc-annexin V uptake was observed in the mid myocardium after 0.5-1.5 h of reperfusion. The area of annexin uptake had expanded in the subendocardial and subepicardial layers at 6 h after reperfusion and then gradually lessened over 3 d. At 0.5 and 1.5 h of reperfusion, 99mTc-annexin V uptake ratios were 7.36 +/- 2.95 and 6.34 +/- 2.24 (mean +/- SD), respectively. The uptake ratios gradually decreased at 6 h, 1 d, 3 d, and 2 wk after reperfusion (4.65 +/- 1.93, 3.27 +/- 0.92 [P < 0.01 vs. 0.5 h], 1.84 +/- 0.55 [P < 0.001 vs. 0.5 h, P < 0.005 vs. 1.5 h], and 1.65 +/- 0.31 [P < 0.001 vs. 0.5 h, P < 0.005 vs. 1.5 h], respectively).


CONCLUSIONS
These data indicate that annexin binding commences soon after ischemia and reperfusion in the mid myocardium within the area at risk and expands to include the subendocardial and subepicardial layers at 6 h after reperfusion, followed by gradual reduction of activity over 3 d.
Taki
Junichi
J
Department of Biotracer Medicine, Kanazawa University Graduate School of Medical Sciences, Kanazawa, Japan. taki@med.kanazawa-u.ac.jp
Higuchi
Takahiro
T
Kawashima
Atsuhiro
A
Tait
Jonathan F
JF
Kinuya
Seigo
S
Muramori
Akira
A
Matsunari
Ichiro
I
Nakajima
Kenichi
K
Tonami
Norihisa
N
Strauss
H William
HW
D000818:Animals; D017304:Annexin A5 / Q000493:pharmacokinetics*; D017209:Apoptosis; D004195:Disease Models, Animal; D008297:Male; D008657:Metabolic Clearance Rate; D017202:Myocardial Ischemia / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D015428:Myocardial Reperfusion Injury / Q000150:complications / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology*; D017682:Myocardial Stunning / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D032383:Myocytes, Cardiac / Q000000981:diagnostic imaging* / Q000378:metabolism* / Q000473:pathology; D015609:Organotechnetium Compounds / Q000493:pharmacokinetics*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D051381:Rats; D017208:Rats, Wistar; D013223:Statistics as Topic; D014018:Tissue Distribution
D017304:Annexin A5; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; C417036:technetium Tc 99m annexin V