Beccavin C, Chevalier B, Cogburn L A, Simon J, Duclos M J
Institut National de la Recherche Agronomique, Centre de Recherche de Tours, Station de Recherches Avicoles, 37380 Nouzilly, France.
J Endocrinol. 2001 Feb;168(2):297-306. doi: 10.1677/joe.0.1680297.
Insulin-like growth factors (IGFs) stimulate growth rate in a number of animal species and are likely to contribute to genetic variations of growth potential. The present study was designed to link levels of IGF-I and IGF-II mRNA and peptides with growth rate in divergently selected genotypes of chickens with high (HG) or low (LG) growth rates. Circulating IGF-I and -II and hepatic mRNA levels were measured under ad libitum feeding conditions from 1 to 12 weeks of age, and at 6 weeks of age under three different nutritional conditions (fed, fasted for 16 or 48 h, re-fed for 4 or 24 h after a 48-h fast). IGF binding proteins (IGFBPs) were also measured. Circulating IGFs increased with age and were higher in HG chickens from 1 to 6 weeks. They decreased with fasting and only IGF-II was fully restored after 24 h of re-feeding, while IGF-I remained low. A significant decrease in steady state IGF-I mRNA levels was also observed with fasting. Across the nutritional study, hepatic IGF-I mRNAs were significantly higher in HG chickens. Variations of IGF-II mRNA levels with nutritional state or genotype exhibited a similar trend. IGFBP (28, 34 and 40 kDa) levels increased with age, while only faint differences were observed between genotypes. IGFBP-28 transiently increased with fasting and was inversely related to blood glucose and insulin levels, suggesting that it is equivalent to mammalian IGFBP-1. In HG chickens, IGFBP-28 and IGFBP-34 levels decreased markedly following re-feeding. Therefore, high and low growth rates were respectively associated with high and low IGF-I and -II levels, supporting the hypothesis of a stimulatory role for both IGFs during post-hatching growth of chickens.
胰岛素样生长因子（IGFs）可刺激多种动物的生长速度，并且可能与生长潜力的遗传变异有关。本研究旨在将IGF-I和IGF-II的mRNA及肽水平与生长速度不同的高生长率（HG）和低生长率（LG）鸡的基因型联系起来。在1至12周龄自由采食条件下，以及在6周龄时处于三种不同营养条件下（正常采食、禁食16或48小时、禁食48小时后再采食4或24小时），测量循环中的IGF-I和 -II以及肝脏mRNA水平。同时也测量了IGF结合蛋白（IGFBPs）。循环中的IGFs随年龄增长而增加，在1至6周龄时HG鸡中的水平更高。禁食时它们会降低，再采食24小时后只有IGF-II完全恢复，而IGF-I仍保持低水平。禁食时还观察到稳态IGF-I mRNA水平显著下降。在整个营养研究中，HG鸡肝脏中的IGF-I mRNA显著更高。IGF-II mRNA水平随营养状态或基因型的变化呈现相似趋势。IGFBP（28、34和40 kDa）水平随年龄增长而增加，而基因型之间仅观察到细微差异。IGFBP-28随禁食短暂增加，并且与血糖和胰岛素水平呈负相关，表明它等同于哺乳动物的IGFBP-1。在HG鸡中，再采食后IGFBP-28和IGFBP-34水平显著下降。因此，高生长率和低生长率分别与高IGF-I和 -II水平以及低IGF-I和 -II水平相关，支持了两种IGFs在鸡孵化后生长过程中起刺激作用的假设。
