穿心莲内酯微乳在大鼠体内的吸收行为研究

Absorption kinetics of andrographolide microemulsion in rats

目的以穿心莲内酯微乳为对象,探讨微乳制剂在大鼠体内的吸收行为。方法采用大鼠原位灌注实验法,测定质量浓度分别为1、2、4、8 g/L,pH值分别为7.8、7.0、6.18、5.4的穿心莲内酯微乳在大鼠胃、十二指肠、空肠、回肠、结肠的吸收率,观察微乳制剂的最佳吸收部位、以及质量浓度、pH值等制剂因素对吸收行为的影响。结果穿心莲内酯微乳在胃部的吸收率随pH值降低而增加,pH值为5.4的吸收率可达40.3%;质量浓度的变化对穿心莲内酯微乳在胃部的吸收率没有显著影响。在小肠的吸收率也随pH值降低而增加,质量浓度的变化对其在整肠的吸收有显著影响,在小肠的吸收能力依次为回肠>结肠>空肠>十二指肠>直肠。结论微乳制剂在胃部有极高的吸收,有pH依赖性,无饱和性,属被动转运;在小肠中的最佳吸收部位集中在小肠中、后段,有pH依赖性和饱和性,吸收机理比较复杂,可能存在2种以上的吸收形式。

Objective To study the absorption kinetics of microemulsion in rats taken andrographolide as study object.Methods The rat model of in situ perfusion was used and the absorption rates of andrographolide microemulsion were detected（the mass concentration of andrographolide was 1 g/L,2 g/L,4 g/L and 8 g/L;pH was 7.8,7.0,6.18 and 5.4,respectively）,in rat stomach,duodenum,jejunum,ileum and colon.The best location for absorption of andrographolide microemulsion and the influences of concentration and pH values on absorption kinetics were studied,and the mechanism was discussed.Results The absorption rate of andrographolide microemulsion increased in stomach as pH decreased,and reached 40.3% when pH was 5.4.The changes of mass concentration had no influence on the absorption rate in stomach.The absorption rate increased in small intestine as pH decreased.The changes of mass concentration had significant influences on the absorption in the whole intestines.The absorption power in small intestine showed a descending order as follows： ileum,colon,jejunum,duodenum and rectum.Conclusion The absorption of microemulsion is greatly higher in stomach with pH reliability but without saturability,which is in a manner of passive transportation.The best absorption location centers in the mid-section and posterior section of small intestine with pH reliability and saturability.The absorption mechanism is complicated and there may be two or more absorption forms.