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-

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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.