Role of somatomedin C in anabolism and catabolism of body proteins

生长抑素C或胰岛素样生长因子-I(IGF-I)是一种多肽类激素，在动物的生长和蛋白质代谢中起重要作用。本研究旨在阐明胰岛素样生长因子-I(IGF-I)在大鼠蛋白质合成代谢和分解代谢中的生理意义：(1)良好营养条件下血浆IGF-I浓度升高，不良营养条件下IGF-I浓度降低；(2)与胰岛素样生长因子结合蛋白(IGFBP)-3结合的血浆IGF-I浓度在良好营养条件下升高。伴随着IGF-I-IGFBP-3复合体的增加，IGFBP-3的血浆浓度也显著升高。相反，在良好的营养条件下，IGFBP-1和IGFBP-2的血浆浓度显著降低。通过测定肝脏中这两种蛋白质的mRNA含量或通过测定肝脏中的mRNA合成速率来探讨这些血浆浓度变化的机制。这些结果为研究IGF-I和IGFBPs在动物蛋白质合成代谢和分解代谢中的作用提供了新的视角。

Somatomedin C, or insulin-like growth factor-I (IGF-I), is a peptide hormone which has been suggested to play an important role in growth and protein metabolism in animals. The present investigations were planned to elucidate the physiological significance of IGF-I in protein anabolism and catabolism in rats.(1) Plasma concentration of IGF-I increased under good nutritional conditions and decreased under poor nutritional conditions.(2) Plasma IGF-I conjugated with insulin-like growth factor binding protein (IGFBP)-3 increased under good nutritional conditions. In concomitant with this increase in IGF-I-IGFBP-3 complex, the plasma concentration of IGFBP-3 increased significantly. On the contrary, plasma concentrations of IGFBP-1 and IGFBP-2 decreased extensively under good nutritional conditions.The mechanisms of these changes in plasma concentrations of IGF-I and IGFBPs were investigated by determining mRNA contents of these proteins in liver or by measuring the rate of mRNA synthesis in liver. The results gave new perspectives concerning the role of IGF-I and IGFBPs in protein anabolism and catabolism in animals.