| This study was conducted to investigate the extraction, structure of Astrugulus polysaccharide (APS) and study the effects of APS on the growth performance and immune system of the weaning pigs. The first experiment is about the extraction and structure of APS. The results showed that APS obtained from extraction solution is composed of two components, one molecular weight determined is 59400 according to the gel chromatography, another is too trace to determine the molecular weigh. The primary polysaccharide is composed of glucose, mannose, fructose, fucose and arabinose according to gas chromatography. The mole ratio of monopolysaccharides is 25.79:0.8:0.63:5.52:1. The second experiment is conducted to study the effects of APS on the antibacterial action in vitro. Four different concentrations of APS (0,0.1%, 0.5% and 1%) were added respectively to four kinds of bacterial: E.coli., Staph.aureus , Salmonella and Pseudomonas aeruginosa. The results showed that the low level of APS did not inhibit the growth of four kinds of bacterial, and 0.5% addition of APS inhibited significantly the growth of E.coli, while the growth of E.coli., Staph.aureus and Salmonella were inhibited by the highest of addition level (1.0%), which suggested that APS possessed the ability of antibacterial effect under the high addition level, but not show the antibacterial action at low addition level of APS. The third experiment was further conducted to study the effects of APS on the growth performance and immune system of weaning pigs. 108 pigs (Large White x Landrace x Pietran) weaned at 28 ?3 d and weighed 7.7 + 0.3 kg were divided into six treatments with a 2 x 3 factorial arrangement. The factors included dietary APS levels (0,500 and 1000 ppm APS) and immunological challenge (LPS or saline). On d 7 and 21, pigs were injected i.p. with either 200 ug/kg BW of LPS or sterile saline. Blood samples were collected for analysis of plasma IL-1B, PGE2, cortisol, GH and IGF-I at 3 h post-injection and at 2 d post-injection for in vitro analysis of blood lymphocyte proliferation and interleukin-2 (IL-2) production. The results showed that LPS challenge decreased the ADG (P < 0.05) and ADFI (P < 0.05) of weaning pigs. APS alleviated the decreased ADG and ADFI. Meanwhile, APS abated the augment of secretion of IL-1(3 (P < 0.05), PGE2 (P < 0.001) and cortisol (P < 0.05) and increased the secretion of IGF-I (P < 0.10). LPS challenge enhanced the lymphocytes proliferation and IL-2 bioactivity, and APS increased linearly the lymphocytes proliferation {P < 0.05) and IL-2 bioactivity (P < 0.05). All the above results demonstrated that APS could abate the decreased growth performance according to not only the decreased secretion of inflammatory cytokines and stress hormone but also to increase immunity of weaning pigs challenged with LPS. In order to elucidate the mechanisms by which APS exerted its effects as an anti- inflammatory agent, the final experiment is conducted to study that peripheral blood lymphocytes of weaning pigs were incubated with APS (0 40 80 160 and 320 ug/mL) to investigate several intracellular signaling molecules such as NO, cAMP, cGMP, Ca2+ and iNOS. The results showed that APS increased the immunity and possessed the anti-inflammation ability according to altered induction of NO, NOS, cAMP, cGMP and Ca2+ dependency on doses of APS. These results suggest APS acts as an anti-inflammatory and immunomodulatory agent due to alteration of intracellular signal transduction. |
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