锌对热应激大鼠POMC衍生肽的影响

EFFECT OF ZINC ON POMC PEPTIDES IN HEAT-STRESSED RATS

大鼠喂饲高锌（ＨＺ）、中锌（ＭＺ）、低锌（ＬＺ）饲料２周后，在高温室（干球４０．５℃，湿球３０．８℃）连续暴露３ｈ，观察锌对阿黑皮素原（ＰＯＭＣ）衍生肽的影响。结果发现：（１）高温刺激可致垂体β－内啡肽（β－Ｅｐ）含量下降、血浆β－Ｅｐ和ＡＣＴＨ浓度升高；（２）在室温下摄入不同锌水平饲料可使大鼠血浆ＰＯＭＣ衍生肽浓度发生变化，高锌摄入有助于增加血浆β－Ｅｐ和ＡＣＴＨ水平，而低锌摄入则使血浆β－Ｅｐ和ＡＣＴＨ水平下降；（３）摄入不同锌水平大鼠经高温暴露３ｈ后，垂体β－Ｅｐ含量下降程度不同（ＨＺ组下降最少，ＭＺ组次之，ＬＺ组下降最多），血浆β－Ｅｐ和ＡＣＴＨ浓度升高也各异（ＨＺ组和ＭＺ组增高较少，ＬＺ组增加最多）。据此结果，还就锌对热应激鼠发挥保护作用的机制进行初步探讨，提出了锌增强机体热耐受能力的假说。

In this study a total of 48 Sprague-Dawley rats were equally divided into 3 groups, i. e. high zinc group(HZ),middle zinc group(MZ), and low zinc group(LZ). The rats in each group were randomly divided into two parts again. One part was used for heat exposure and the other for room temperature control. According to the grouping, rats were fed with high zinc diet, middle zinc diet and low zinc diet in room temperature for 2 weeks respectively. Then the rats for heat exposure were placed in climatic chamber (Tdb 40.5 ℃,Twb 30.8 ℃)for 3 hours. β-Ep levels in rats plasma were determinded by radioimmunoassay. The findings showed as follows. (1) Heat stimulation could decrease β-Ep and ACTH levels in plasma. (2) In room temperature ,different zinc intake could change POMC peptides concentrations in rat plasma. High zinc diet could help to raise plasma β-Ep and ACTH levels than low zinc diet. (3) After heat exposure for 3 hours, β-Ep contents in pituitaries of rats fed different zinc diets decreased more or less whereas β-Ep and ACTH concentrations in plasma increased. A possible protective mechanism of diet zinc against heat stress were discussed.