^(99)Tc^m-HL91在大鼠缺血脑内分布的放射自显影观察

Autoradiography observation on the dynamic distribution of ^(99)Tc^m-HL91 in the rat model of focal cerebral ischemia

目的探讨99Tcm-4,9-二氮-3,3,10,10-四甲基十二烷-2,11-二酮肟(HL91)在大鼠局灶性脑缺血脑内的动态分布规律。方法用线栓法建立大鼠局灶性脑缺血模型,SD大鼠42只分为2组:①预处理脑缺血组(21只),脑缺血预处理20min,再灌注3d后再次脑缺血2h;②脑缺血组(21只),脑缺血2h。两组按再灌注时间不同(5、30min及1、2、4、8、12h)又各分为7个亚组,每组3只。用γ测量和放射自显影方法,观察99TcmHL91在大鼠局灶性脑缺血脑内的动态分布规律。结果γ测量结果示,注药后5min～2h,两组患侧与健侧脑组织单位质量放射性比值(TNT)均为1.0左右,差异无显著性(P>0.05);注药后4h两组TNT明显增加,4、8、12h预处理脑缺血组TNT分别为1.57±0.13、1.93±0.06、2.25±0.17,与同组2h比较,差异均有显著性(P均<0.01),脑缺血组TNT分别为1.22±0.12、1.59±0.07、1.94±0.09,与同组2h比较,差异均有显著性(P<0.05～0.001);注药后4、8、12h预处理脑缺血组与脑缺血组间两两比较,差异均有显著性(P均<0.05)。放射自显影结果示,注药后5min～2h,两组患侧和健侧脑组织银颗粒主要分布于细胞间质和毛细血管中,细胞内分布较少;注药后4h,两组患侧银颗粒主要分布于脑组织神经细胞内,而细胞间质和毛细血管内分布较少;两组8、12h亚组分布规律与4h亚组相同;

Objective To study the dynamic distribution of 99Tcm-4,9-diaza-3,3,10,10-tetramethyldodecan-2,11-dione dioxime (HL91) in the rat model of focal cerebral ischemia. Methods Rat model of focal cerebral ischemia and ischemia-reperfusion was established by suture-occluded method. 42 SD rats were equally divided into 2 groups: ①Preconditioned cerebral ischemic group: middle cerebral artery was occluded for 20 min, then reperfused for 3 d and occluded again for 2 h. ②Cerebral ischemic group: middle cerebral artery was occluded for 2 h only. Both groups were divided into 7 sub-groups (5, 30 min and 1,2,4,8,12 h) according to the different time duration of the reperfusion. γ-counting and autoradiography were used to observe the dynamic distribution of 99Tcm-HL91. Results ①γ-counting: 5 min～2 h after the injection of 99Tcm-HL91, the radioactivity ratios of cerebrum per weight (T/NT) indicated that there were no significant differences between the ischemic side and the healthy side in both groups (P>0.05), T/NT was about 1.0. 4 h after the injection, the radioactivity of cerebrum ratios per weight increased significantly in both groups. T/NT was 1.57±0.13, 1.93±0.06, 2.25±0.17 respectively at 4, 8, 12 h after the injection in preconditioned cerebral ischemic group, the radioactivity ratios showed significant differences (P<0.01) compared with the ratio of 2 h. 4～12 h after the injection, T/NT was 1.22±0.12, 1.59±0.07, 1.94±0.09 respectively in cerebral ischemic group, the radioactivity ratios also showed significant differences (P<0.05～0.001) compared with the ratio of 2 h. T/NT ratios at 4, 8, 12 h after the injection showed significant differences (P<0.05) between preconditioned cerebral ischemic group and cerebral ischemic group. ②Autoradiography: 5 min～2 h after the injection ,silver granules distributed mainly in intercellular matrix and capillary, only a few within cells both in ischemic and healthy side of the two groups. From 4 h to 12 h silver granules distributed mainly in the neuronal cells of ischemic side and only a few in intercellular matrix and capillary. The density of silver granules of ischemic side in preconditioned group was higher than that in ischemic group. Conclusions 99Tcm-HL91 was distributed prominently in ischemic cerebrum 4～12 h after injection, and 99Tcm-HL91 in the preconditioned ischemic cerebrum was significantly higher than the non-preconditioned one. Hence, it is suitable to perform cerebral imaging 4 h after the injection in clinical practice.