Leili S, Buonomo F C, Scanes C G
Department of Animal Sciences, Rutgers-State University of New Jersey, New Brunswick 08903, USA.
Proc Soc Exp Biol Med. 1997 Oct;216(1):104-11. doi: 10.3181/00379727-216-44162a.
The effect of feed (energy/protein) restriction on circulating concentrations of insulin-like growth factor (IGF)-I and II, and IGF-binding proteins (IGFBPs) was examined in young (4-week-old) chickens. Increasing levels of feed restriction caused progressive growth retardation, as evidenced by decreased body-weight gain and reduced bone growth. Plasma concentrations of both IGF-I and IGF-II were decreased, and the degree of reduction in the plasma concentrations of these growth factors appeared to be related to the magnitude of feed restriction. A tendency for greater decreases in these growth factors appeared to be associated with greater feed restriction at the majority of time points evaluated. However, nutritional restriction had a greater effect on plasma concentrations of IGF-I than on those of IGF-II. The reductions in plasma concentrations of IGF-I were observed earlier in the experiment and at a lower degree of nutritional deprivation than for plasma concentrations of IGF-II, possibly suggesting greater sensitivity of IGF-I plasma concentrations to feed restriction. Three IGFBPs with molecular weights of 30, 36, and 40 kDa were detected by radioligand assay following separation by SDS-electrophoresis. The 30-kDa IGFBP was most affected by feed restriction with binding activity of this IGFBP increased by 2 days of feed restriction irrespective of the degree of feed deprivation. The binding activity of the 36-kDa IGFBP was increased, albeit transiently, on the second day of feed restriction. Nutritional restriction had no discernible effect on the binding activity of the 40-kDa IGFBP. Increases in the binding activity of the 30-kDa IGFBP appeared to correspond with the observed decreases in IGF-I plasma concentrations. This suggests decreased bioavailability of IGF-I, and possibly IGF-II, attributed to the formation of a complex between IGF-I and the 30-kDa IGFBP during feed restriction. The initial increase in binding activity of the 36-kDa IGFBP may suggest that this binding protein also plays a role in the regulation and availability of circulating concentrations of IGF-I and IGF-II. Although the binding activity of the 40-kDa IGFBP was unaffected by feed restriction, we can not exclude its importance in the regulation of IGF-I. The substantial binding activity of the 40-kDa IGFBP observed in this experiment suggests that it is one of the major chicken IGFBPs, and that its role in IGF-I regulation warrants further study.
在4周龄的幼鸡中研究了饲料（能量/蛋白质）限制对胰岛素样生长因子（IGF）-I、IGF-II以及IGF结合蛋白（IGFBP）循环浓度的影响。饲料限制水平的增加导致渐进性生长迟缓，体重增加减少和骨骼生长减缓证明了这一点。IGF-I和IGF-II的血浆浓度均降低，这些生长因子血浆浓度的降低程度似乎与饲料限制的程度有关。在大多数评估的时间点，这些生长因子更大程度的降低趋势似乎与更严重的饲料限制有关。然而，营养限制对IGF-I血浆浓度的影响大于对IGF-II血浆浓度的影响。与IGF-II的血浆浓度相比，在实验早期且营养剥夺程度较低时就观察到了IGF-I血浆浓度的降低，这可能表明IGF-I血浆浓度对饲料限制更为敏感。通过SDS电泳分离后，采用放射性配体测定法检测到三种分子量分别为30、36和40 kDa的IGFBP。30 kDa的IGFBP受饲料限制的影响最大，无论饲料剥夺程度如何，饲料限制2天后该IGFBP的结合活性就会增加。36 kDa的IGFBP的结合活性在饲料限制的第二天虽短暂增加。营养限制对40 kDa的IGFBP的结合活性没有明显影响。30 kDa的IGFBP结合活性的增加似乎与观察到的IGF-I血浆浓度的降低相对应。这表明由于在饲料限制期间IGF-I与30 kDa的IGFBP形成复合物，导致IGF-I以及可能还有IGF-II的生物利用度降低。36 kDa的IGFBP结合活性的最初增加可能表明该结合蛋白在调节IGF-I和IGF-II的循环浓度及其可用性方面也发挥作用。尽管40 kDa的IGFBP的结合活性不受饲料限制的影响，但我们不能排除其在IGF-I调节中的重要性。在本实验中观察到的40 kDa的IGFBP的大量结合活性表明它是鸡主要的IGFBP之一，其在IGF-I调节中的作用值得进一步研究。
