高原低氧对大鼠左乙拉西坦药代动力学特征及脑血分布的影响

Effects of plateau hypoxia on pharmacokinetic parameters and cerebral-blood distribution of levetiracetam in rats

目的:高原低氧暴露易引起药物药动学参数及脑血分布的改变,其中包括多种P糖蛋白(P-glycoprotein,P-gp)的底物。抗癫痫药物左乙拉西坦是P-gp的底物,但高原低氧暴露是否改变其药代动力学特征及脑血分布尚不明确。本研究旨在探讨高原低氧对大鼠左乙拉西坦药代动力学特征及脑血分布的影响。方法:将Wistar大鼠分为低海拔对照组、高海拔组、溶剂对照组和P-gp诱导组,其中高海拔组大鼠急性暴露于4010 m高原环境24 h后口服或静脉注射左乙拉西坦,口服给药后分别于第0.083、0.25、0.5、0.83、1.25、2、4、6、8、10、12、24 h采集血浆,静脉注射给药后分别于第5、45、60、120、240 min采集血浆及脑组织;P-gp诱导组大鼠连续3 d腹腔注射地塞米松后,静脉注射左乙拉西坦,于第120 min采集血浆及脑组织。采用高效液相色谱串联质谱(high performance liquid chromatography-tandem mass spectrometry,HPLC-MS/MS)测定血浆和脑内药物浓度,采用蛋白质印迹法检测大鼠血脑屏障P-gp的表达。结果:与低海拔对照组相比,高海拔组大鼠左乙拉西坦药时曲线下面积(area under the curve,AUC)下降14.69%(P<0.01),平均驻留时间(mean residence time,MRT)下降15.42%(P<0.01),血浆清除率(clearance,CL)升高16.67%(P<0.01),静脉注射给药后第5、45、120、240 min的脑/血药物浓度比分别降低22.82%(P<0.05)、12.42%(P<0.05)、17.40%(P<0.01)和13.22%(P<0.01),血脑屏障P-gp表达升高86.3%(P<0.05);与溶剂对照组相比,P-gp诱导组大鼠血脑屏障P-gp表达升高56.3%(P<0.05),脑/血药物浓度比下降19.3%(P<0.05)。结论:急性高原低氧暴露改变了左乙拉西坦在大鼠体内的药代动力学特征,并降低了其在大鼠体内的脑血分布。左乙拉西坦脑血分布的下降可能与血脑屏障P-gp的表达上调有关。

Objective:Plateau hypoxia exposure causes changes in pharmacokinetic parameters and cerebral-blood distribution of drugs,including many substrates of P-glycoprotein(P-gp).Levetiracetam,a kind of antiepileptic drugs,is a substrate of P-gp.Whether plateau hypoxia exposure changes its pharmacokinetic characteristics and cerebral-blood distribution remains unclear.This study aims to investigate the effects of plateau hypoxia on the pharmacokinetics and cerebra-blood distribution of levetiracetam.Methods:Wistar rats were divided into a low-altitude control group,a high-altitude group,a solvent group,and a P-gp induction group.After 24 h of exposure at altitude of 4010 m,rats in the high-altitude group were given levetiracetam orally or intravenously.The plasma was respectively collected at 0.083,0.25,0.5,0.83,1.25,2,4,6,8,10,12,and 24 h after oral administration of the drug,while both plasma and brain were respectively collected at 5,45,60,120 and 240 min after intravenous injection.After 3 days administration of dexamethasone,plasma and brain of rats in the P-gp induction group were collected at 120 min after intravenously giving levetiracetam.Plasma and brain concentrations of the drug were determined by high performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS).The expression of P-gp in blood-brain barrier was detected by Western blotting.Results:Compared with the low-altitude control group,the area under the curve(AUC)and mean residence time(MRT)of levetiracetam were respectively decreased by 14.69%(P<0.01)and 15.42%(P<0.01),while the clearance(CL)was increased by 16.67%(P<0.01)in the high-altitude group.The ratio of brain/blood plasma drug concentration was decreased by 22.82%(P<0.05),12.42%(P<0.05),17.40%(P<0.01),and 13.22%(P<0.01)at 5,45,120,and 240 min after injection,respectively.The expression of P-gp on the blood-brain barrier was increased by 86.3%(P<0.05).Compared with the solvent control group,the expression of P-gp on the blood-brain barrier in the P-gp induction group was increased by 56.3%(P<0.05),the ratio of brain/blood plasma drug concentration was decreased by 19.3%(P<0.05).Conclusion:After acute plateau hypoxia exposure,the pharmacokinetic of levetiracetam in rats are altered,and the cerebral-blood distribution of the drug in rats is decreased,which may be related to the up-regulation of P-gp expression on the blood-brain barrier.