Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA 24061, USA.
Poult Sci. 2012 Aug;91(8):1941-9. doi: 10.3382/ps.2011-02092.
Chick embryos derive nutrients from the yolk during incubation and transition to intestinal absorption of nutrients posthatch. The uptake of nutrients is mediated by a variety of membrane-bound transporter proteins. The objective of this study was to determine the expression profiles of nutrient transporters and digestive enzymes during incubation in the yolk sac membrane (YSM) and embryonic intestine of egg-laying (Leghorn) and meat-producing (Cobb) chickens derived from 22 to 30 wk (young) and 45 to 50 wk (old) breeder flocks. Transporters examined included the peptide transporter PepT1, the glutamate/aspartate (EAAT3), cationic (CAT-1) and neutral (B0AT) amino acid transporters, and the fructose (GLUT5) and glucose (SGLT1) transporters. Digestive enzymes included aminopeptidase N (APN) and sucrase-isomaltase (SI). Expression of these genes was assessed by real-time PCR using the absolute quantification method in YSM at embryonic day (E) 11, 13, 15, 17, 19, 20, and 21 and intestine at E15, 17, 19, 20, and 21. The PepT1 and APN gene expression in the YSM increased until E15 and then decreased until E21, whereas expression in the intestine increased from E15 to E21. The B0AT showed a similar pattern, with greatest expression in the YSM occurring at E17/E19. The CAT1 and GLUT5 genes showed decreased expression in the YSM and increased expression in the intestine until E17/E19 and then a decrease until E21. Expression of SGLT1 and EAAT3 showed increased gene expression over time in both the intestine and YSM. Expression of SI showed little to no gene expression in the YSM, whereas the intestine exhibited consistently high levels of gene expression. In YSM and intestine, SI expression was greater in Leghorn than Cobb, whereas CAT1 and GLUT5 expression was greater in Cobb than Leghorn. Expression of the APN, CAT1, and SI genes was greater in embryos from young flocks than old flocks in YSM and intestine. These results demonstrate that the YSM expresses many of the digestive enzymes and nutrient transporters typically associated with the intestine and that these genes show tissue- and development-specific patterns of expression.
在孵化过程中，鸡胚从卵黄中获取营养物质，并在孵化后通过肠道吸收营养物质。营养物质的吸收是由多种膜结合转运蛋白介导的。本研究的目的是确定在产蛋（来亨鸡）和肉用（考伯鸡）鸡的卵黄囊膜（YSM）和胚胎肠中，从 22 到 30 周龄（年轻）和 45 到 50 周龄（年老）种鸡群中，在孵化期间以及在 YSM 和胚胎肠中，营养转运体和消化酶的表达谱。研究的转运体包括肽转运体 PepT1、谷氨酸/天冬氨酸（EAAT3）、阳离子（CAT-1）和中性（B0AT）氨基酸转运体以及果糖（GLUT5）和葡萄糖（SGLT1）转运体。消化酶包括氨肽酶 N（APN）和蔗糖酶-异麦芽糖酶（SI）。通过实时 PCR 用绝对定量法在 YSM 中于胚胎日（E）11、13、15、17、19、20 和 21 以及肠中于 E15、17、19、20 和 21 进行基因表达的评估。YSM 中的 PepT1 和 APN 基因表达在 E15 之前增加，然后在 E21 之前减少，而在肠中从 E15 增加到 E21。B0AT 表现出相似的模式，最大表达发生在 E17/E19。CAT1 和 GLUT5 基因在 YSM 中的表达减少，在肠中表达增加，直到 E17/E19，然后减少到 E21。SGLT1 和 EAAT3 的表达在 YSM 和肠中随着时间的推移表现出基因表达增加。SI 在 YSM 中几乎没有基因表达，而肠中则表现出持续高水平的基因表达。在 YSM 和肠中，Leghorn 比 Cobb 的 SI 表达更高，而 Cobb 的 CAT1 和 GLUT5 表达更高。在 YSM 和肠中，年轻鸡群的胚胎中的 APN、CAT1 和 SI 基因表达高于年老鸡群。这些结果表明，YSM 表达了许多与肠相关的消化酶和营养转运体，这些基因表现出组织和发育特异性的表达模式。
