Research On Absorption And Transport Of Dipeptide In Small Intestine Of Laying Hen In Vitro

Research on small peptide had become hotspot in the field of nutrition and biology for its advantages of absorption and transport, as well as the special function of physiology and pharmacology. This research was the absorption and transport of dipeptide in small intestine of laying hen in vitro. The content of dipeptide and amino acid was measured by high performance liquid chromatograph (HPLC) and ion chromatograph. This study including three experiments:Exp.1．The experiment on absorption and transport of Gly-Gly,Gly-L-Leu and Met-Gly in small intestine of laying hen in vitro: Small intestine was separated into five segments: duodenum, proximal jejunum, middle jejunum, distal jejunum and ileum. Each intestine segment are 8~10 cm, which were everted and cleaned with PBS solution, sacs prepared from various intestine segments were then transferred into 5 different treatment solutions: plain PBS solution as control, 20 mmol/L mixture of glycine and leucine PBS solution(Gly+Leu) and 20mmol/L three kinds of dipeptide PBS solution. Cultured at 39.5℃ for 30min, sample was taken from chorion fluid, tissue homogenate and mucous membrane fluid in every intestinal segments, dipeptide and free amino acid content was examined by ion chromatograph. The results showed: Gly from three kinds of dipeptide content was significantly higher than that from Gly+Leu (P<0.05) in chorion fluid and tissue; Gly content from three kinds dipeptide was different and its turn is Gly-Gly>Gly-L-Leu>Met-Gly; Leu content from Gly-L-Leu was 60.43％ higher than that from Gly＋Leu(P<0.05) ; And the rate of absorption and transport Gly and Leu in the ileum was highest; intact dipeptide could not be detected. These results implied that absorption and transport of Gly and Leu from dipeptide is more efficient than that from mixture of free glycine and leucine; the most effective absorption and transport for Gly and Leu was occurred in the ileum; and there was hydrolysis or transform of dipeptide in small intestine curture in vitro. Exp2.This study on hydrolysis of Gly-Gly and Gly-L-Leu of intestinal peptidase: method based on Exp.1, peptidase inhibitor (Bestatin and Amastin) was used; 20mmol/L Gly-Gly and Gly-L-Leu as control, and each kind's dipeptide solution was treated with inhibitor as test group. Culture at 39.5℃ for 25min and sample was taken every 5min and measured dipeptide content in incubation medium by HPLC. Gly-Gly couldn't be detected in both groups and control group after 5min; Gly-L-Leu content in test group decreased by 56.6%, but in control group decreased by 83.25%; in test group Gly-L-Leu content was slightly different (P>0.05) from 10min to 25min, about 8mmol/L; Total content of Gly-L-Leu was significantly difference between test group and control one (P<0.05). These findings explained: intestinal peptidase was released quickly into the culture medium and hydrolyzed dipeptide. Bestatin and Amastatin could inhibit the hydrolysis of Gly-L-Leu, but not to Gly-Gly. Exp.3 Experiment on effect of peptidase inhibitor on absorption and transport of Gly-L-Leu. test method see Exp1. Experiment was divided into two groups. Group 1 peptidase inhibitor was added to mucosal not to chorion fluid; Group 2 was opposition. Culture at 39.5℃ for 15min, we measured the content of dipeptide and amino acid in mucosal membrane, chorion and tissue fluid in different intestine parts by ion chromatogram. The results showed Gly-L-Leu content was higher in group 1 than group 2(P<0.05), and its content in mucosal fluid was significantly higher than that in chorion and tissue (P<0.05). There was no statistical difference in Gly-L-Leu content at different intestine parts in group 1; Gly-L-Leu could not be measured in all intestinal sacs except in ileum in group 2. Gly-L-Leu content in both groups was the highest in ileum chorion and tissue. Conclusion: only a small quantity of intact Gly-L-Leu could be absorbed and transported quickly by intestines tissue; the absorption and transport of intact Gly-L-Leu mostly occurred in ileum. Intestinal...