Tomas F M, Knowles S E, Chandler C S, Francis G L, Owens P C, Ballard F J
Cooperative Research Centre for Tissue Growth and Repair, Child Health Research Institute, Adelaide, South Australia.
J Endocrinol. 1993 Jun;137(3):413-21. doi: 10.1677/joe.0.1370413.
Administration of IGF-I over a 14-day period to growing female rats via s.c. implanted osmotic pumps led to an increased body weight gain, an improved N retention and a greater food conversion efficiency. The effects were dose-dependent, with the highest daily dose tested, 278 micrograms/day, producing 18-26% increases in these measurements. LR3IGF-I, a variant of human IGF-I that contains an amino terminal extension peptide as well as glutamate-3 replaced by arginine and exhibits very weak binding to IGF-binding proteins, was substantially more potent than the natural growth factor, in the 44 micrograms/day of this peptide produced similar effects to the high IGF-I dose. Organ weight and carcass composition measurements showed that the two IGF peptides generally maintained body proportions at those existing when the experiment began. Muscle protein synthesis and myofibrillar protein breakdown were both slightly increased by IGF treatment, so that the observed improvement in N retention could not be explained through protein accretion rates calculated from these measures. Infusion of human GH at a dose of 213 micrograms/day did not stimulate body growth. This investigation establishes that IGF peptides stimulate the growth of normal growing animals, with IGF-I variants that bind less well to IGF-binding proteins being more active than IGF-I.
通过皮下植入渗透泵对生长中的雌性大鼠进行为期14天的IGF-I给药，导致体重增加、氮保留改善和食物转化效率提高。这些作用呈剂量依赖性，所测试的最高日剂量为278微克/天，这些测量值增加了18 - 26%。LR3IGF-I是人类IGF-I的一种变体，含有一个氨基末端延伸肽以及被精氨酸取代的谷氨酸-3，并且与IGF结合蛋白的结合非常弱，其效力明显高于天然生长因子，该肽每天44微克产生的效果与高剂量IGF-I相似。器官重量和胴体组成测量表明，这两种IGF肽通常使身体比例维持在实验开始时的水平。IGF处理使肌肉蛋白质合成和肌原纤维蛋白质分解均略有增加，因此，通过这些测量计算出的蛋白质积聚率无法解释所观察到的氮保留改善情况。以每天213微克的剂量输注人生长激素不会刺激身体生长。这项研究证实，IGF肽能刺激正常生长动物的生长，与IGF结合蛋白结合较差的IGF-I变体比IGF-I更具活性。
