稳定性核素测定大鼠小肠蛋白质合成

Measurement of small intestine protein fractional synthesis rates with stable isotope

目的:建立稳定性核素([L1-5N]亮氨酸)测定大鼠小肠蛋白质合成率的方法。方法:分别测定静脉注射相同剂量[L1-5N]亮氨酸不同时相的大鼠小肠15N丰度及不同剂量[L1-5N]亮氨酸同一时相的大鼠小肠15N丰度。结果:大鼠小肠游离氨基酸池中15N核素丰度在注射后0.5 h内呈线性上升并达高峰,维持4 h后缓慢下降,小肠蛋白质中的15N丰度0.5 h至12 h基本维持不变;随着注射剂量的增加,大鼠小肠蛋白质分数合成率(FSR)亦增加,当[L1-5N]亮氨酸剂量在1.0mmol/kg以上,FSR并不随施加[L1-5N]亮氨酸剂量的加大而增加。结论:在进行大鼠小肠蛋白质合成率测定时,一次性静脉注射的测量最佳时限为0.5 h,剂量为1.0mmol/kg。

Objective： To develop a new technique for measuring synthesis rates of small intestinal protein in rats with [ L-^15 N ] Leucine. Methods ： After intravenous injection of [ L-^15 N ] Leucine , the enrichment of ^15 N in different time intervals with the same dosage and at fixed time by various dosage were measured. Results： During the period from 0 to 30 minutes, there is nearly a linear increase in enrichment of ^15N of free amino-acid pool to the peak in rats＇small intestine. For bond amino-acid pool, the level of enrichment of ^15N is at its plateau between 0.5 and 12 hours with the increase of dosage, FSR did not rise with the increasing dosage of more than 1.0 mmol/kg of [ L-^15N] Leucine, there is no significant discrepancy. Conclusion ： For measuring synthesis rate of small intestine protein in rats, 30 minutes after mainlining is optimal and the most suitable dosage of [ L-^15N] Leucine is 1.0 mmol/kg.