［8F］FDG microPET在评价二次打击所致大鼠急性肺损伤中的应用

目的：对一次打击和二次打击进行深入的对比研究，应用［8F］-氟脱氧葡萄糖（FDG）小动物正电子断层扫描仪（microPET）对肺内的炎症反应进行评价。方法: 将33只SD雄性大鼠随机分为4组，分别为生理盐水 (NS) 组（n=3）：生理盐水1 mL/kg腹腔注射(ip)及16 h后生理盐水0.5 mL/kg气道内滴入（it）；脂多糖(LPS)组（n=10）：LPS 5 mg/kg ip及16 h后生理盐水0.5 mL/kg it；HCl组（n=10）:生理盐水1 mL/kg ip及16 h后HCl（pH=1.2,0.5 mL/kg,it）；二次打击 LPS-HCl 组（n=10）：LPS 5 mg/kg ip及16 h后HCl（pH=1.2,0.5 mL/kg,it）。在盐酸或生理盐水气道滴入前，所有大鼠戊巴比妥钠腹腔注射麻醉，行股动脉插管，连续监测平均动脉压（MAP），并于it后0.5 h、1.5 h及4 h后抽血，查动脉血气分析，it后4 h行［8F］FDG micro PET 胸部扫描，然后处死动物，取肺组织进行组织病理学观察。结果: 血气分析显示LPS-HCl大鼠低氧血症和二氧化碳潴留显著；MAP在气道内滴入盐酸或生理盐水前无差异，但在滴入后，LPS-HCl 组中MAP较其它3组显著降低；microPET示感兴趣区（ROI）在右肺与右上肢肌肉之间的比值进行比较，LPS-HCl 组中此比值为 9.00±1.41,显著高于LPS组4.01±0.60（P<0.01)和HCl组3.33±0.55 (P<0.01)；肺损伤病理评分在 LPS-HCl 组中为12.70±0.95,显著高于 HCl组8.40±1.26（P<0.01）和LPS组7.00±0.82 (P<0.01)。结论:二次打击可使机体肺内产生剧烈而且持久的炎症反应，比一次打击更容易诱发急性肺损伤；microPET作为一种无创的检测手段，能很好地评价急性肺损伤时肺内的炎症反应。

Evaluation of the inflammatory response in two -hit acute lung injury model of rats using [18SF]FDG microPET

AIM: To investigate whether two-hit acute lung injury (ALI) model is better than one-hit, and to evaluate the inflammatory response in the lungs during these models by using ［8F］FDG microPET. METHODS: Thirty three, adult, male Sprague-Dawley rats weighing 180-210 g were used and divided into 4 groups. Rats in LPS group (n=10) and LPS-HCl group (n=10) were challenged with intraperitoneal administration of LPS at the dose of 5 mg/kg, while rats in NS group (n=3) and HCl group (n=10) received normal saline solution intraperitoneally at the dose of 1 mL/kg, after 16 h, all animals were anesthetized with an intraperitoneal injection of sodium pentobarbital (40 mg/kg) and placed in a 60°inclined position, the femoral artery was cannulated and connected to a pressure transducer to record the arterial pressure on a polygraph recorder, the trachea was surgically exposed. Rats in HCl group and LPS-HCl group received direct intratracheal injection of HCl (pH=1.2) at the dose of 0.5 mL/kg while rats in NS group and LPS group received the same volume of normal saline solution. Blood gas samples (each 0.3 mL) were obtained at 30, 90 and 240 min after the instillation and replaced by the same volume of saline solution, the samples were analyzed using a blood gas analyzer. 240 min after HCl or NS administration, the rats underwent a microPET scanning, then, all the rats were sacrificed and the lungs were obtained for histological analysis. RESULTS: Blood gas analysis showed that rats in LPS-HCl group had higher PaO2 and lower PaCO2 than the other groups. MAP decreased markedly in LPS-HCl group, while MAP in other groups remained stable. The results of microPET showed that the ratio of ROI between the right lung and the muscle tissue of the right arm in LPS-HCl group was 9.00±1.41, and was significantly higher than that in LPS group (4.01±0.60) and HCl group (3.33±0.55). Histological examination showed that the mean lung injury score in LPS-HCl group was 12.70±0.95, while that was 8.40±1.26 in HCl group and 7.00±0.82 in LPS group, and there were significant differences (both P<0.01). CONCLUSION: LPS pretreatment significantly magnifies and prolongs the inflammatory response to the subsequent acid instillation in both lungs. When compared with “one-hit”, “two-hit” is easier to induce the ALI, and ［8F］FDG microPET is a useful tool to evaluate the inflammatory reaction during ALI.