Effect protein deficiency on lnsulin like growth factor-I and lnsulin like growth factor-II gene expression physiological reles of lnsulin like growth factors as a local factore in growing lambs-

为研究蛋白质营养与骨生长的关系机制，分别饲喂蛋白质缺乏饲粮和对照饲粮，采用RT-PCR法检测生长软骨中胰岛素样生长因子- 1和胰岛素样生长因子- ii的基因表达。另外用放射免疫法测定血浆胰岛素样生长因子- 1和胰岛素样生长因子- ii的浓度。体重约20 kg的雄性阉割羔羊按双反转设计分为两组。分别饲喂粗蛋白质含量为17.5%的对照组饲粮和蛋白质缺乏型饲粮（粗蛋白质含量为4.9%）。这些日粮的能量含量满足其需求。蛋白质缺乏抑制体重增加。血浆胰岛素样生长因子- 1浓度降低。与胰岛素样生长因子- 1相比，各组血浆胰岛素样生长因子- 2浓度均显著降低。血浆胰岛素样生长因子- ii不受蛋白质缺乏的影响。生长软骨中胰岛素样生长因子- 1的转录有因蛋白质缺乏而减少的趋势，但这种变化并不显著。然而，生长软骨中胰岛素样生长因子- ii的转录不受蛋白质缺乏的影响。这些结果表明，蛋白质缺乏通过降低血浆胰岛素样生长因子- 1浓度和生长软骨中局部产生的胰岛素样生长因子- 1来抑制骨生长。然而，血浆胰岛素样生长因子- ii和局部产生的胰岛素样生长因子- ii与蛋白质缺乏羊骨生长迟缓无关。

To study the mechanism of relationship between protein nutrition and bone growth, growing lambs were fed protein deficient diet or control diet and the gene expression of lnsulin like growth factor-I and lnsulin like growth factor-II were measured by RT-PCR in the growth cartilage. Additionally plasma concentrations of lnsulin like growth factor-I and lnsulin like growth factor-II were determined by dadio immunoassay. Male castrated lambs weighing approximately 20 kg were allotted to two groups in a double reversal design. These animals were fed control diet (crude protein content ; 17.5%) or protein deficient diet (crude protein content, 4.9%) . Energy contents in these diets satisified for its requirement. Protein deficiency suppressed body weight gain. Plasma insulin like growth factor-I concentration was lowered When lambs were fed the protein deficient diet. Compared to lnsulin like growth factor-I, plasma lnsulin like growth factor-II concentration was remarkably low in each group. And plasma lnsulin like growth factor-II was not affected by protein deficiency. Transcript of lnsulin like growth factor-I in the growth cartilage tended to be reduced by protein deficiency though this change was not significant. However, transcript of lnsulin like growth factor-II in the growth cartilage was not affected by protein deficiency. These results suggested that protein deficiency suppressed bone growth through reducing plasma lnsulin like growth factor-I concentration and locally produced lnsulin like growth factor-I in the growth cartilage. However, plasma lnsulin like growth factor-II and locally produced lnsulin like growth factor-II were not related to the retardation of bone growth in protein deficient sheep.