Objective To establish a practical microPET imaging procedure for the measurement of myocardial metabolic rate of glucose (MRGlu) in mice.Methods Twenty wild-type BKS mice were divided into 4 groups by random number table method.The mice were anesthetized with different concentrations of isoflurane (1.3％,1.5％,1.8％,2.0％) at the temperature between 30 ℃ to 34 ℃.The respiratory rate and the physiologic condition were monitored for adjusting the most appropriate isoflurane concentration.Then,different volumes of saline were injected to the anesthetized mice and blood glucose concentrations were measured to test the optimal injection volume.Under the optimal operating condition,18 F-FDG were injected in a group of six mice and followed by microPET imaging.Left ventricular TAC was obtained by drawing ROI and myocardial glucose SUV was also calculated.Meanwhile,the TAC from venous sampling at different time points after 18F-FDG injection was generated."Kinetic Imaging System" was used to estimate the coefficients and calculate the MRGlu(Ki ×Glu/LC; Ki =k1 ×k3/(k2+k3).One-way analysis of variance and q test were used to analyze the data.Results No movement was observed in non-fasted mice anesthetized with (1.5-1.8)％ isoflurane,and their respiratory rates were all over 80 per minute.The plasma glucose concentration showed no difference at each time point between the experimental group injected with 75 μl saline and the control group (F=1.215,P＞0.05).The plasma glucose concentration of mice injected with 150 μl saline exhibited statistically significant difference at 30 min (q =2.485,P=0.024),45 min (q =2.287,P=0.036) and 60 min (q =2.709,P =0.015).When the injection volume reached 300 μl,the blood glucose concentration increased remarkably at 45 min (q =2.435,P=0.027).Mice were maintained in good condition after injected with 18F-FDG ranging from 7.4 to 11.1 MBq within 75 μl volume,meanwhile clear and stable myocardial microPET images could also be obtained.The median myocardial SUV value was 11.88(9.71-14.93),Ki value was 0.19 (0.10-0.54) ml · min-1 · g-1and MRGlu value was 19.64 (5.55-23.28) mg · kg-1 · min-1at 45-55 min after 18F-FDG injection.Conclusion The microPET imaging may be a reliable,practical method to evaluate myocardial glucose uptake rate and metabolic rate in mice under the precondition of optimal isoflurane anesthetization (1.5％-1.8％)and small volume of 18F-FDG injection (≤＜75 μl).%目的 建立适合的microPET测定小鼠心肌葡萄糖代谢率(MRGlu)的实验方法和条件,并评价该方法的可行性.方法 控制温度在30～ 34℃,取正常进食的野生型BKS小鼠20只,按随机数字表法分为不同异氟烷体积分数(1.3％、1.5％、1.8％和2.0％)麻醉组,观察小鼠呼吸频率及存活状态,获得最佳浓度;另取BKS小鼠20只,在最佳异氟烷浓度麻醉下,注射不同体积(0、75、150、300 μl)生理盐水,观察各组小鼠血糖变化,获得最适宜注射体积.取BKS小鼠6只,在最佳异氟烷浓度麻醉下,注射最适宜体积18 F-FDG,对小鼠心肌行microPET显像,通过勾画ROI获取心肌TAC,计算SUV.同时,经小鼠尾静脉多点采血获取尾静脉TAC,利用输入函数数学模型显像分析系统,获得代谢速率常数k1,k2,k3,k4,计算心肌MRGlu:MRGlu=Ki ×Glu/LC[Ki=k1×k3/(k2+k3),Glu为平均血糖浓度,LC为集总常数(心肌取1)].数据比较采用单因素方差分析和q检验.结果 小鼠在正常进食的情况下,以体积分数1.5％～1.8％异氟烷麻醉,小鼠呼吸频率在80次/min以上,无任何体位移动.注射生理盐水75μl组小鼠在不同时间点的血糖与不注射生理盐水相比,差异均无统计学意义(F=1.215,P＞0.05).150μl组小鼠血糖在30 min(q=2.485,P=0.024)、45 min(q=2.287,P=0.036)、60 min(q=2.709,P=0.015)与0μl组差异均有统计学意义;300ul组小鼠血糖在45 min(q=2.435,P=0.027)与0山组差异有统计学意义.18F-FDG注射体积≤75止、剂量为7.4～11.1 MBq时,micro-PET显像可获得小鼠相对接近生理状态下的清晰稳定图像,45～55 min小鼠心肌SUV中位数为11.88(范围9.71～14.93),K值中位数为0.19(范围0.10～0.54) ml·min-1·g-1,MRGlu值中位数为19.64(范围5.55～23.28) mg·kg-1· min-1.结论 在microPET18F-FDG显像评估小鼠心肌葡萄糖摄取及代谢率过程中,适宜异氟烷麻醉体积分数为1.5％～1.8％,18F-FDG注射体积需≤75 μl;该方法切实可行.
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