| Objective: There is no widely commended oral method of removal of intestinal ammonia for prevention and treatment of hepatic encephalo- pathy(HE). The main problem is that current methods have no direct ability to remove ammonia and the clearance rate is low. In this study,we investigated the direct effect on removing colon ammonia by Micro- Emulsion for Removal of Ammonia(ME-RA),as well as by Microemulsion- Based Gels for Removal of Ammonia(MBGs-RA) which is established on the basis of ME-RA for improving removal of ammonia and the stability in gastrointestinal tract and for its pH intellectualized orientation towards colon. We hoped that it would provide a new method for prevention and treatment of HE and even for removal of other intestinal toxins.Methods:1.ME-RA of the water-in-oil(W/O) microemulsion formulation was prepared with span80 and tween80 etc. as surfactant, ethylene glycol as cosurfactant, simethicone as extra-oil and 30 percent of acetic acid as inner phase. MBGs-RA was established by adding intelligent high polymer of Alginic Acid based on ME-RA.2.The artificial gastric fluid,intestinal fluid and colon fluid were prepared according to the Chinese Pharmacopoeia 2005 Edition. Put ME-RA in the artificial colon fluid containing ammonia for ten hours,while putting ME-RA in the artificial gastric fluid for two hours fllowed by artificial intestinal fluid for three hours and finally in the colon fluid for ten hours. After stratifying,we detected the ammonia in the colon fluid referring to the methods of international standards and calculated the clearance rate of ammonia. The removal effeciency for ammonia between the ME-RA and Lactulose was compared by use of a device for detecting ammonia.3.The effeciency of removing ammonia by ME-RA and MBGs-RA was compared after putting them in the artificial gastric juice,and then intestinal fluid and colon fluid referring to the methods as 2; the morphology of ME-RA and MBGs-RA after statifying were observed; the pH of artificial gastrointestinal fluid was monitored.4.18 rats for ME-RA and MBGs-RA respectively were divided into 3 groups randomly containing 6 in each group to study the stability in the gastrointestinal tract stepwise. Group 1:Put a T-tube connecting the stomach and duodenum. The gastric contents were collected at 10min,20min,30min,60min and 120min after administrating ME-RA or MBGs-RA to the stomach. Group 2:Put a T-tube connecting the small intestine and caecum to collect the effluent from the end of the small intestine. Group 3:Collect the anal emissions. We observed the morphology of ME-RA/MBGs-RA by the microscope, measured the size by micrometer scale and detected the pH of gastrointestinal before and after administrating.Results:1.ME-RA could directly remove ammonia in the artificial colon fluid containing ammonia and the removal rates were high,100±0.00% and 97.29±2.67% respectively in artificial colon fluid containing ammonia 10g/L or 20g/L.After digested by the artificial gastric fluid and small intestinal fluid,the clearance rates were 96.41±0.84% and 86.42±2.63% respectively, also a satisfying efficiency, but declined comparing with the ME-RA without digestion and both P values were less than 0.05.2.ME-RA showed more effective than lactulose obviously when comparing the abilities to remove ammonia in vitro(P<0.05).3.MBGs-RA played much better role on removing ammonia in the artificial colon fluid under the environment of simulated whole gastroin- testinal transit and pH. The clearance rates by ME-RA and MBGs-RA were 51.9±1.85% and 55.92±4.76% in artificial colon fluid containing 10g/L ammonia(P<0.05).4.Comparison of their stabilities between ME-RA and MBGs-RA in simulant gastrointestinal environment in vitro(1)The form of ME-RA was stable in artificial gastric fluid and intestinal fluid after swelling and changing into emulsion in artificial gastric fluid. MBGs-RA was stable in artificial gastric fluid and small intestinal fluid and released ME-RA in the artificial colon fluid.(2)Both ME-RA and MBGs-RA had no influence on the pH of the artificial gastric fluid. They could decrease the pH of artificial intestinal fluid and both P values were less than 0.05, but the impact of MBGs-RA reduced significantly vs. ME-RA(P<0.05). Both of them made the pH of the artificial colon fluid lower and both P values were less than 0.05,while the impacts were similar(P>0.05).5.Comparison of their stabilities between ME-RA and MBGs-RA in rat gastrointestinal tract environment(1)The average particle size of ME-RA was less than 1μm. It became swelling and the size of milk droplets fluctuated in 30min and unchanged from 30min to 120min after administered into rat stomach. It deformed and became smaller in the small bowl. The size of MBGs-RA had no significant change and maintained integrity in stomach from 20min to 120min as well as in small intestine. Intact W/O droplets could be seen discharged from colon.(2)The pH of normal rat stomach maintained stable form 20min to 120min by administrating ME-RA but from 10min to 120min by MBGs-RA, and both P values were greater than 0.05. ME-RA could decrease the pH of normal rat small intestine(P<0.05)while MBGs-RA had no significant influence on it(P>0.05). Both of them had no significant effect on the pH of colon, and both P values were greater than 0.05.Conclusion:1.ME-RA could directly and effectively remove ammonia in artificial colon fluid.2.ME-RA could decrease the pH value of small intestine in both simulant and normal rat gastrointestinal tract. It deformed and became smaller in small intestine of rats. It showed that ME-RA had poor stability in the gastrointestinal tract.3.MBGs-RA could remain stable in stomach and small intestine. It could release ME-RA in the colon for enhancing the clearance rate of ammonia so as to realize intellectualized orientation towards colon. This study will provide experimental basis to feedback and further optimize the production of ME-RA and MBGs-RA.
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