| The study was conducted to investigate the effects of Arg-Gly-Gln on the intestine of weaned piglets. It was divided into three trials and a single-factorial design was employed in each.28-day-old weaned piglets were selected to get the sample for jejunum culture in vitro. Trial 1 was conducted to study the stability of tripeptide (0.56mmol/L Arg-Gly-Gln) in the jejunum of weaned piglets. The absorption and transportation differences of glutamine existing as Arg-Gly-Gln, Gly-Gln and free Gln were studied in trial 2. Everted jejunal sacs (both ends were ligated) were assigned to 4 groups. The four treatments were designed as following:Group 1(G1), Kreb's solution +0.56mmol/L Arg-Gly-Gln; group 2 (G2), Kreb's solution + 0.56mmol/L Gly-Gln and Arg; group3 (G3), Kreb's solution + 0.56mmol/L arginine, glycine and glutamine to Kreb's solution; group 4 (G4, control group), Kreb's solution. In trial 2, all the treatments were cultured for 40 minutes. Trial 3 was conducted to study the effects of Arg-Gly-Gln on the jejunum of weaned piglets. Jejunum tissues were assigned to 6 treatments (T0～T5) with 8 replicates each, each replicate containing 1 jejunum tissues. Jejunum tissues were cultured by adding 0 (TO), 0.28 (T1),0.56 (T2),1.11 (T3),2.23 (T4) and 4.45 mmol/L (T5) Arg-Gly-Gln to culture solution.The concentration of Arg-Gly-Gln in trial 1 was gradually decreased from time 0 to 40min, and downed to the lowest level at time 40min. Arg-Gly-Gln was not totally hydrolyzed in jejunum segments of weaned piglets during the culture time. It can be exisited as integral form.In trial 2, as for the serosal fluid and tissue samples, the Arg-Gly-Gln concentrations in G1 were significantly higher than those of G3 and G4 (P<0.05), the Gly-Gln concentrations in G2 were significantly higher than those of G3 and G4 (P<0.05). Absorption ratio of glutamine in G1 (80.20%±1.54%) was higher than those of both G2 (62.57%±3.11%) and G3 (39.07%±1.29%) (P<0.05). The total amount of Gln in serosal fluid of G1 existing as Arg-Gly-Gln, Gly-Gln and free Gln was significantly higher than that of both G2 and G3 (P<0.05). The results suggested that the Gln's absorption and transportation of Arg-Gly-Gln was better than that of Gly-Gln and the latter was better than free Gln.The results of trial 3 showed that Arg-Gly-Gln can down regulate the LDH activity of the culture solution. There was no significant difference between the tissue protein content (P≥0.05). As for the BrdU-positive cell percent, there was no significant difference between TO and T1, the rest treatments presented significant differences as the following: T5>T4>T3>T2 (P<0.05). Arg-Gly-Gln concentration of culture solution and BrdU-positive cell percent was highly significantly correlated (P<0.01) with a coeffeicient of 0.866. The Caspase-3 positive cell percent was decreased along with the increase of Arg-Gly-Gln concentration. There was a highly significantly correlation (P<0.01) between Arg-Gly-Gln concentration and Caspase-3 positive cell percent with-0.796. In addition, as for the activities of glutaminase and diamine oxidase, there were no significant difference among T0, T1 and T2 (P<0.05). Compared to T0, the glutaminase activity of T3, T4, T5 increased 27.69%,46.15% and 83.08%(P<0.05) respectively; the DAO activity increased 66.34% and 110.89%(P<0.05).These results of this study indicated that jejunum of weaned piglets can ingest Arg-Gly-Gln and Gly-Gln in integral forms. Arg-Gly-Gln can facilitate the metabolism of Gln, promote jejunum of weaned piglets' cell proliferation and inhibit the apoptosis of jejunal mucosal cells. And so, it can improve the intestinal adaptation of weaned piglets under the condition of this study.
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