Karcher D M, Fleming-Waddell J N, Applegate T J
Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA.
Growth Horm IGF Res. 2009 Feb;19(1):31-42. doi: 10.1016/j.ghir.2008.05.003. Epub 2008 Jul 15.
Numerous researchers have evaluated the insulin-like growth factors (IGF) influence on mammalian fetal development. Although IGF has been explored in the avian system, questions remain on the role of IGF in avian development. Therefore, the current study evaluated the mRNA abundance of IGF in the amnion and allantoic membranes and developing small intestine in the chicken, duck, and turkey during the incubation and post-hatch period.
Broiler, duck, and turkey eggs were incubated with small intestinal, allantoic, and amniotic membranes collected in the final days of incubation and 1 week post-hatch. RNA was extracted using Trizol and qRT-PCR was utilized to compare differences during embryo development within and across species.
The expression of the IGF mRNA varied between species in the final days of incubation in the amniotic and allantoic membranes. The turkey had higher (0.38-1.72 log) transcript abundance of IGF-I and IGF-II in the amnion and allantois compared to the chicken and duck. Evaluating the mRNA abundance within the chicken duodenum, jejunum, and ileum, the duodenum had the lowest expression of IGF-I and IGF-II (P<0.05) at day -4 of incubation compared to the jejunum and ileum. Focusing on differences in jejunal IGF expression among the three species, the turkey had the lowest IGF-I abundance at day -4 of incubation and highest IGF-I abundance at day of hatch (P<0.05). Transcript abundance of both IGF-II and IGF-R was highest in the turkey at day of hatch and day 1 post-hatch compared to the duck and chicken. The whole tissue versus the mucosal expression of the IGF mRNA abundance was evaluated during the post-hatch period. Duodenal, jejunal, and ileal segments had higher IGF-I transcript abundance (P<0.05) at day 1, day 3, and day of hatch, respectively. No differences were observed between segment and mucosa for IGF-II in the post-hatch period. The duodenal and jejunal mucosa IGF-R transcript abundance was greater (P<0.05) at day of hatch compared to the intestinal segment. The duck IGF mRNA in the jejunal mucosa was higher than the whole segment and decreased from day of hatch to day 3 post-hatch while the IGF mRNA abundance increased in the whole segment during the same time period. The turkey IGF-I transcript abundance decreased in both the segment and mucosa following hatch while the IGF-II mRNA expression increased by 1.5 logs from hatch to day 1 post-hatch.
The transcript abundance of the IGF axis in the extra-embryonic membranes and gastrointestinal tissue of the developing chicken, duck, and turkey are influenced by embryonic age and species. A better understanding of the IGF axis in the small intestine during embryonic development may allow for increasing the optimal growth of both the gastrointestinal tract and the neonate.
众多研究人员已评估胰岛素样生长因子（IGF）对哺乳动物胎儿发育的影响。尽管IGF已在禽类系统中得到研究，但关于IGF在禽类发育中的作用仍存在疑问。因此，本研究评估了鸡、鸭和火鸡在孵化期和出壳后羊膜、尿囊膜及发育中的小肠中IGF的mRNA丰度。
将肉鸡、鸭和火鸡蛋孵化，并收集孵化末期和出壳后1周的小肠、尿囊膜和羊膜。使用Trizol提取RNA，并利用qRT-PCR比较物种内和物种间胚胎发育过程中的差异。
在孵化末期，羊膜和尿囊膜中IGF mRNA的表达在不同物种间存在差异。与鸡和鸭相比，火鸡羊膜和尿囊中IGF-I和IGF-II的转录本丰度更高（0.38 - 1.72对数）。评估鸡十二指肠、空肠和回肠内的mRNA丰度，与空肠和回肠相比，十二指肠在孵化第-4天时IGF-I和IGF-II的表达最低（P<0.05）。关注三种物种空肠中IGF表达的差异，火鸡在孵化第-4天时IGF-I丰度最低，出壳时最高（P<0.05）。与鸭和鸡相比，火鸡在出壳时和出壳后第1天IGF-II和IGF-R的转录本丰度最高。在出壳后时期评估了IGF mRNA丰度的全组织表达与黏膜表达。十二指肠、空肠和回肠段在出壳第1天、第3天和出壳时分别具有较高的IGF-I转录本丰度（P<0.05）。出壳后时期，IGF-II在段和黏膜之间未观察到差异。与肠段相比，十二指肠和空肠黏膜IGF-R转录本丰度在出壳时更高（P<0.05）。空肠黏膜中的鸭IGF mRNA高于全段，从出壳到出壳后第3天下降，而同期全段中的IGF mRNA丰度增加。火鸡出壳后，段和黏膜中的IGF-I转录本丰度均下降，而IGF-II mRNA表达从出壳到出壳后第1天增加了1.5对数。
发育中的鸡、鸭和火鸡的胚外膜和胃肠道组织中IGF轴的转录本丰度受胚胎年龄和物种的影响。更好地了解胚胎发育过程中小肠中的IGF轴可能有助于促进胃肠道和新生儿的最佳生长。
