镁的不同摄入水平对生长期大鼠钙、磷、镁代谢及骨骼的影响

目的　研究饲料缺镁或高镁对生长期大鼠钙、磷、镁吸收代谢以及骨骼发育的影响。方法　 30只 SD大鼠 ,分为三组 ,每组 1 0只 ,单独喂养在有机玻璃代谢笼中 ,第一组大鼠饲喂缺镁饲料 (含镁 86mg/kg) ,第二组饲喂适量镁饲料 (含镁 548mg/kg) ,第三组为高镁饲料 (含镁540 2 mg/kg) ,三组饲料均为人工半合成制备 ,其中含钙 3.7g/kg,含磷 4g/kg。经过 2 5天对喂养方法及代谢笼的适应后 ,开始 5天期的代谢实验。每天记录大鼠的进食量 ,分别收集每个大鼠的粪、尿。代谢实验结束后 ,禁食 1 2 h,在乙醚麻醉下 ,心脏采血并处死大鼠 ,取股骨、胫骨测定重量、长度和体积后 ,与肾脏一起储存于 - 2 0℃ ,待测钙、镁和磷的含量。结果　缺镁和适量补镁对钙的表观吸收基本没有影响 (86% ) ,饲料中过量的镁使大鼠钙的表观吸收略有下降 (83% ) ,高镁使尿钙排出显著增加 ,降低了钙在体内的滞留 ;饲料高镁使磷的表观吸收显著下降。但尿磷排出减少 ,磷在体内滞留反而增加。随着饲料中镁含量的增加 ,粪和尿中镁的排泄均大幅度上升 ,可见镁的内环境稳定由肠道和肾脏共同调节。结论　低镁和高镁饲料均不利于生长期大鼠骨骼的生长发育。低镁饲料使大鼠肾钙、磷蓄积 ,可能是肾结石形成的主要原因。

THE INFLUENCE OF DIFFERENT DIETARY MAGNESIUM LEVELS ON THE METABOLISM OF CALCIUM, PHOSPHOROUS AND MAGNESIUM AND DEVELOPMENT OF BONE IN GROWING RATS

Objective: To study the effect of dietary magnesium deficiency and excess on the metabolism of calcium, phosphorus and magnesium as well as the develompent of bone in growing rats. WT5FZ]Methods:WT5BZ] 30 male Sprague Dawley rats were divided into three groups, 10 per group and housed in non metal metabolic cages individually. The rats in the first group were fed Mg deficient diet (Mg 86 mg/kg), the rats in the second group were fed Mg adequate diet (mg 548 mg/kg), while in the third group fed Mg excess diet (Mg 5 402 mg/kg). All the diets were semi synthetic containing Ca: 3.7 g/kg,P: 4 g/kg. After 25 days feeding and adaptation to the metabolic cages, the five day period metabolic experiment was carried out. The daily food intakes were recorded and the samples of feces and urine were collected respectively. At the end of the period, fasting blood samples were taken from heart under light anesthesia. The femur and tibia were dissected, and after measuring weight, length and volume, stored together with kidney at -20℃ until analysis for Ca,Mg and P. WT5FZ]Results:WT5BZ] There was no much influence on the apparent absorption of Ca (86%) when Mg was deficient or adequate, and Mg excess in diet made Ca absorption decrease a little(83%). However, Mg excess increased urinary Ca excretion significantly so that the retention of Ca was decreased. Meanwhile, Mg excess significantly decreased apparent absorption of P, but the retention of P increased due to the lower urinary P excretion. With the increase of Mg contents in diet, Mg excretion in feces and urine increased significantly, this meant the homeostasis of Mg was regulated by intestine and kidney. WT5FZ]Conclusion: Both Mg deficiency and excess are detrimental to the skeletal growth and development in growing rats. Mg deficient diet leads to accumulation of Ca and P in kidney, probably involving in the pathogenesis of nephrolithiasis.