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目的:研究L-[1-13C]苯丙氨酸呼气试验(PheBT)结果与大鼠肝脏苯丙氨酸羟化酶(PAH)活性的关系. 方法:CCl4诱导急性肝损伤SD大鼠10只,正常对照组10 只;尾静脉给予13C标记L-苯丙氨酸(13C-phe)20 mg/kg, 收集给药前和给药后60 min内间断时间点的气样:采用气体同位素比值质谱仪测量气样中13CO2丰度;计算呼气气中13C清除速率常数;采用酶偶联法测量肝脏组织中PAH活度. 结果:绝大部分正常(9/10)和CCl4急性肝损伤(8/10)大鼠尾静脉给予13C—phe以后,呼出气中13C排除在2 min 达到峰值;呼出气中13C排除分为快、慢两个时相;CCl4 肝损伤大鼠PheBT参数13C排除速率常数PheBT—k显著小于正常对照组(P=0.00,P<0.01),其值分别为(2.45±0.25)×10-2/min和(2.98±0.19)×10-2/min而快时相13C 处置常数在肝损伤和正常组大鼠之间没有差异(P>0.05), 其值分别为(9.46±3.27)×10-2/min和(10.17±2.10)×10-2/min; CCl4急性肝损伤大鼠呼出气中13C丰度峰值(204.33±35.80)‰却显著高于正常对照组(170.65±22.85)‰(P= 0.04,P<0.05);急性肝损伤大鼠全肝脏苯丙氨酸羟化酶活度显著低于正常对照组(P=0.00,P<0.01);大鼠呼气试验参数PheBT—k与大鼠全肝苯丙氨酸羟化酶总活度高度相关(r=0.92,P=0.00,P<0.001). 结论:PheBT时全肝PAH总活度降低是急性肝损伤大鼠呼出气中13C排除速率下降的最直接原因:呼气试验参数PheBT—k可以定量评价肝脏损伤程度.
Aims: To study the relationship between the results of L-1- (1-13C) phenylalanine breath test (PheBT) and the activity of hepatic phenylalanine hydroxylase (PAH) in rats.Methods: CCl4-induced acute liver injury in rats Only normal control group of 10; the tail vein was given 13C labeled L-phenylalanine (13C-phe) 20 mg / kg, before and 60 min after administration to collect gas samples at the time of discontinuation: the use of gas isotopes Ratio 13CO2 abundance in gas samples was measured by mass spectrometry, 13C removal rate constants in exhaled breath were calculated, and activity of PAH in liver tissues was measured by enzyme coupling method.Results: Most of the normal (9/10) and CCl4-induced acute liver injury (8/10) rats after tail vein administration of 13C-phe, exhaled 13C exclusion peak at 2 min; exhaled 13C exclusion is divided into fast and slow phase; CCl4 liver injury rat PheBT parameters 13C excluded The rate constant PheBT-k was significantly lower than that of the normal control group (P = 0.00, P <0.01) and the values were (2.45 ± 0.25) × 10-2 / min and (2.98 ± 0.19) × 10-2 / min respectively The phase 13C treatment constant had no difference between the liver injury group and the normal group (P> 0.05), and the values were (9.46 ± 3.27) × 10-2 / min and (10.17 ± 2.10) × 10-2 / min, respectively. CCl 4 acute liver injury in exhaled air 13 (204.33 ± 35.80) ‰ was significantly higher than that of the normal control group (170.65 ± 22.85) ‰ (P = 0.04, P <0.05). The activity of phenylalanine hydroxylase in the whole liver of rats with acute liver injury was significantly (P = 0.00, P <0.01). PheBT-k was significantly correlated with total liver phenylalanine hydroxylase activity in rats (r = 0.92, P = 0.00, P <0.001) .Conclusion: The decrease of total activity of PAH in PheBT is the most direct reason for the decrease of 13C elimination rate in exhaled breath of rats with acute liver injury: the parameter of expiratory test PheBT-k can quantitatively evaluate the extent of liver injury.