高锌饲料对大鼠胸腺发育及其作用机理的探讨

EFFECT OF HIGH DIETARY ZINC ON THE DEVELOPMENT OF THYMUS AND ITS MACHANISM IN RATS

通过建立大鼠高锌（ＺＨ）模型，研究高锌对胸腺发育的影响及其作用机理。结果表明：（１）ＺＨ组的体重、体重增长值、饲料效价均非常显著低于配对（ＰＦ）组；（２）ＺＨ组的血清、毛发、股骨及胸腺细胞锌含量均非常显著地高于ＰＦ组；（３）ＺＨ组的胸腺重量、胸腺指数、胸腺细胞大小、胸腺肽含量和胸腺素活性，均非常显著地低于ＰＦ组；（４）ＺＨ组的胸腺细胞内ＤＮＡ、蛋白质含量低于，而Ｇ１／Ｇ０期细胞（％）数高于ＰＦ组；（５）ＺＨ组胸腺细胞内ｃＡＭＰ、ｃＡＭＰ／ｃＧＭＰ比值非常显著高于ＰＦ组，增殖指数（ＰＩ）与ｃＡＭＰ、ｃＡＭＰ／ｃＧＭＰ比值呈负相关；与ｃＧＭＰ呈正相关，均Ｐ＜０．０１；（６）ＺＨ组血清钙低于ＰＦ组，而胸腺细胞内Ｃａ２＋高于ＰＦ组，Ｐ＜０．０５。结果提示，适量锌有促进胸腺发育、增殖的作用，而高锌则反之。其机理可能是高锌影响细胞内腺苷酸环化酶系统，并与胞浆内游离钙和钙调蛋白的调节活性有关。

The effect of high dietary zinc on the development of thymus and its mechanism were investigated in rats.The findings were as follows:(1)The body weight,weight gain and feed efficiency value of high dietary zinc group(ZH) were significantly lower than those of pair fed group(PF).(2)Zinc contents of serum,hair,femur and thymocytes in ZH group were significantly higher than those in PF.(3)The weight and the cell size of thymus,thymus index,thymus peptide content and thymin activity were significantly lower in ZH group than those in PF group.(4)In ZH group,DNA and protein contents of thymocytes were lower but the G 0/G 1 phase of cell cycle of thymus were significantly higher than those in PF group.(5)cAMP level and cAMP/cGMP ratio of the thymoctyes were significantly higher in ZH group than those in PF group.The level of cAMP and the cAMP/cGMP ratio showed significantly negative correlation with proliferative index,but the level of cGMP showed significantly positive correlation with PI,P<0.01.(6)As compared with PF group serum calcium was significantly lower in ZH group and the level of calcium ion of thymocytes was higher,P<0.05.It was concluded that adequate dietary zinc could promote the development and proliferation of thymus,but excessive amount of zinc could depress such function.It is posible that high dietary zinc can affect the regulating activity of adenyl cyclase system,calcium ion and calmodulin in the thymoctyes.