Kita K, Tomas F M, Owens P C, Knowles S E, Forbes B E, Upton Z, Hughes R, Ballard F J
Cooperative Research Centre for Tissue Growth and Repair, Adelaide, South Australia.
J Endocrinol. 1996 Apr;149(1):181-90. doi: 10.1677/joe.0.1490181.
We have examined the influence of nutrition on plasma IGF-I, IGF-II and IGF-binding protein (IGFBP) levels and on hepatic IGF-I gene expression in young meat-type chickens. Plasma IGF concentrations were measured by using RIA with recombinant chicken IGFs as standards. In chickens fed the control diet containing 200 g/kg dietary protein ad libitum for 7 days, plasma IGF-I concentrations increased significantly from those found in the initial control group. Food restriction for either 4 or 7 days decreased plasma IGF-I by 30% from the initial control. When chickens were refed ad libitum for 3 days after 4 days of restricted feeding, plasma IGF-I levels recovered to those of the control birds fed ad libitum. In chickens eating a low protein diet (100 g/kg protein), the plasma IGF-I tended to be lowered but the decrease was not significant. Although the intensity of IGF-I and beta-actin mRNA bands protected in the RNase protection assay was changed by nutrition, no statistical effect of nutrition on the ratio of IGF-I to beta-actin was observed. The nutritional treatments had no effect on plasma IGF-II concentrations. Western ligand blot and chromatographic analyses were used to investigate the influence of nutrition on IGFBP profiles. Both IGF-I and IGF-II ligands in the Western ligand blot revealed the most intense binding at 30 kDa for plasma obtained from chickens with restricted food intake. The 30 kDa band also appeared at a lower intensity in the group fed a low protein diet but not in any other groups. These observations were confirmed by neutral gel chromatography. The chicken IGF-II ligand revealed an intensely labelled band corresponding to 75 kDa and this was not affected by nutrition. IGF-I and IGFBP concentrations in the plasma of young broiler chickens were influenced by nutritional state but IGF-II concentrations were not. The lack of a response in circulating IGF-II levels may have been due to the presence of high concentrations of a 75 kDa specific binding protein which did not respond to nutrition in this experiment.
我们研究了营养对肉用仔鸡血浆胰岛素样生长因子-I（IGF-I）、胰岛素样生长因子-II（IGF-II）和胰岛素样生长因子结合蛋白（IGFBP）水平以及肝脏IGF-I基因表达的影响。血浆IGF浓度采用以重组鸡IGF为标准品的放射免疫分析法（RIA）进行测定。在自由采食含200 g/kg日粮蛋白质的对照日粮7天的鸡中，血浆IGF-I浓度较初始对照组显著升高。禁食4天或7天使血浆IGF-I浓度比初始对照组降低30%。在限饲4天后再自由采食3天，血浆IGF-I水平恢复到自由采食的对照鸡的水平。采食低蛋白日粮（100 g/kg蛋白质）的鸡，其血浆IGF-I有降低趋势，但降低不显著。尽管在核糖核酸酶保护试验中受保护的IGF-I和β-肌动蛋白mRNA条带强度因营养而改变，但未观察到营养对IGF-I与β-肌动蛋白比值有统计学意义的影响。营养处理对血浆IGF-II浓度无影响。采用Western配体印迹法和色谱分析法研究营养对IGFBP谱的影响。Western配体印迹法中，IGF-I和IGF-II配体在采食量受限鸡的血浆中均显示在30 kDa处结合最强。在采食低蛋白日粮组中30 kDa条带强度也较低，但在其他组中未出现。中性凝胶色谱法证实了这些观察结果。鸡IGF-II配体显示出一条对应于75 kDa的强标记条带，且不受营养影响。肉用仔鸡血浆中的IGF-I和IGFBP浓度受营养状态影响，但IGF-II浓度不受影响。循环中IGF-II水平缺乏反应可能是由于存在高浓度的75 kDa特异性结合蛋白，在本实验中该蛋白对营养无反应。
