The results showed that APP can significantly improve the relative level of IgA and this is also consistent with the results about the increased content of SIgA which can be formed by IgA. given 50 mg/kg body weight/day of APP, APP-L), a APP medium-dose group (injected with Cy, given 200 mg/kg body weight/day of APP, APP-M), a APP high-dose group (injected with Cy, given 500 mg/kg body weight/day of APP, APP-H) and a positive control group (injected with Cy, given with 50 mg/kg body weight/day of thymosin enteric-coated tablets, PC). All of the mice had free access to standard rodent chow and cleaning water, and were given test substance once a day for 27 days. All groups except NC group were intraperitoneally injected with Cy (50 mg/kg body weight/day), and the NC group was injected with an equal volume of sterile saline on the 25th and 26th day. All mice were fasted for 24 h and blood was taken on the 27th day. At the end of the experiments, mice were euthanized by cervical dislocation. This study was approved by the ethical committee of experimental animal care at College of Food Science and Engineering in Ocean University of China (Qingdao, China). All animal experiments were performed follow the guidelines of National Institutes of Health guide for the PF-04971729 care and use of Laboratory animals (NIH Publications No. 8023, revised 1978). 2.6. Thymus Index and Spleen Index of Mice The body weight of the mice was weighed every other day during the breeding period. PF-04971729 Balb/c mice were euthanized after fasted (keep the supply of drinking water) for 24 h, and then the thymus and spleen were excised separately to weight. The filter paper were used to absorb the surface liquid. Thymus index = (thymus mass (mg)/body weight (g)) 10 (1) Spleen index = (spleen mass (mg)/body weight (g)) 10 (2) 2.7. H&E Staining The segments of intestinal jejunum (1C2 cm length) were fixed in 4% ( 0.05. 3. Results and Discussion 3.1. Amino Acid Composition of APP The amino acid composition of APP was shown in Table 2. Gly, Glu, Ala, Lys, and Asp were rich in APP, similar to that of peptide from Pacific cod and Atlantic salmon [21,22]. Essential amino acids (Leu, Thr, Ile, Phe, Lys, Met, Val, Trp) of APP accounted for 30.8% of the total amino acids and branched-chain amino (Ile, Val, Leu) occupied 40.6% of the essential amino acids. Peptides with abundance of glutamine were frequently used to improve the immunity of the small intestine and the supplementation of branched-chain amino acid played an important role on the immune response [23,24]. According to the reference protein suggested by FAO/WHO Mouse monoclonal to Cytokeratin 19 [25], the chemistry scores of essential amino acids were more than 0.8, which indicated that APP can be used as a good source of quality protein. Thus, supplements of APP could provide nutrition support for various metabolic activities to improve the small intestinal immunity [26,27]. Table 2 Amino acid compositions of Alaska Pollock peptide (APP) (mol/1000 mol). 0.01), which suggested that Cy had an effect on the weight reduction of immune organs. The APP-H group can improve the spleen index and thymus index in immunocompromised mice PF-04971729 induced by Cy ( 0.05); however they were not up to the normal level, which indicated that APP could improve the immune organ index of mice with low immunity but cannot reverse the atrophy of thymus and spleen. The results were consistent with the PF-04971729 previous study [8]. It was reported that many bioactive substances can enhance the immunity by increasing the organ index, such as pineal peptide, collagen peptide from jelly fish, and squid ink polysaccharide [30,31,32]. Open in a separate window Figure 1 The change of spleen index (A), thymus index (B) and morphology of small intestine (C) in mice. Values are expressed as mean SD, = 10. The different symbols indicate significant differences (# 0.05, ## 0.01 compared to the NC group; * 0.05, compared to the Cy group). PF-04971729 3.4. Histological Assessment of the Intestinal Mucosa Cy could cause low immunity, while the intestinal tract as the bodys immune organ.