自消容子水提取物对大鼠的毒性作用及肝损伤机制的初步研究

目的:研究含吡咯里西啶生物碱中草药自消容子的水提取物对大鼠的急性毒性、主要毒性靶器官及其肝损伤作用的初步机制,探讨该药材临床用药的安全性.方法:按传统水提醇沉法制备自消容子水提取物,进行急性毒性试验,采用寇氏法计算该提取物对大鼠的LD50.设定高、中、低3个剂量组和对照组对大鼠进行灌胃给药,单次给药后观察7d,7d末进行生化指标测定和组织病理学检查.进一步采用体外肝微粒体代谢方法进行实验,结合以上研究探讨其肝毒性机制.结果:自消容子水提取物灌服Wistar大鼠的LD50为(2.36 ±0.26)g·kg-1.不同剂量给药组大鼠均出现毒性反应,其中,血清转氨酶(ALT和AST)较对照组均有显著升高,组织病理学检查显示大鼠肝、肺脏有明显损伤,其程度亦呈剂量依赖性.研究还发现,肝组织结合吡咯在给药组大鼠均有形成且呈剂量依赖性的增加,同时,体外肝微粒体代谢实验也检测出吡咯代谢物,提示了肝代谢与毒性的发生具有一定的相关性.结论:自消容子具有较强的急性毒性作用；肝、肺是其主要的毒性靶器官；肝损伤作用机制与药材所含吡咯里西啶生物碱的代谢活化及其组织共价结合有关.

Toxic effects of aqueous extract of Crotalariae Assamicae Semen in rats and possible mechanism in association with liver damage

Objective: To study the toxic effects of aqueous extract of Crotalariae Assamicae Semen (CAS), one of the pyrrolizidine alkaloid-containing Chinese herbal medicines, in rats and the possible mechanism in association with liver damage. Method: The aqueous extract of CAS (CASE) was prepared by the conventional water extracting-alcohol precipitating method. The LD₅₀ value of CASE in rats was determined by Kärber method. Rats were randomly divided into four groups in which three groups were orally administered with different doses of the CASE and one group with distilled water as control. Toxic effects were assessed by morphological, biochemical and histopathological changes. Moreover, in vitro metabolism using rat liver microsomes was also conducted and applied for the exploration of the underlying mechanism of liver damage. Result: The LD₅₀ value of CASE in Wistar rats was (2.36±0.26) g·kg^-1. The toxic effects were found in all groups of rats dosed with CASE, in which serum levels of ALT and AST were significantly elevated, and the obvious and dose-dependent damages in liver and lung were observed by histopathological examination. Moreover, the liver tissue-bound pyrroles were detected and generated in a dose-dependent manner, and the pyrrole metabolites observed in the in vitro microsomal metabolism. All the evidences suggested a strong correlation between metabolism and toxicity of CASE in rats. Conclusion: CASE could induce the acute toxicity in rats, of which liver and lung were the major targets. Toxic effects were strongly correlated with pyrrolizidine alkaloids in CAS. The possible mechanism for its liver toxicity may be related to the formation of pyrrole metabolites as well as the corresponding tissue-binding products.