Takeuchi Ken, Bjarnason Ingvar, Laftah Abas H, Latunde-Dada Gladys O, Simpson Robert J, McKie Andrew T
Division of Internal Medicine, Diabetes and Endocrinology, King's College, London SE5 9PJ, UK.
Scand J Gastroenterol. 2005 Feb;40(2):169-77. doi: 10.1080/00365520510011489.
The large intestine has been reported to have a capacity for iron absorption and expresses genes for iron absorption normally found in the duodenum. The importance and function of these genes in the large intestine are not understood. We therefore investigated the cellular localization and regulation of expression of these genes in mouse caecum and colon.
Gene expression was measured by real-time PCR using RNA extracted from iron-deficient and hypoxic mouse large intestine, compared to controls. Protein localization and regulation were measured by immunohistochemistry using frozen sections of the large intestine from the same mice.
Dcytb (duodenal ferric reductase) was expressed at very low levels in the large intestine, compared to the duodenum, while Ireg1 and DMT1 were expressed at significant levels in the large intestine and were increased in iron-deficient caecum, proximal and distal colon, with the most significant increases seen in the distal colon. Hypoxia increased Ireg1 expression in the proximal colon. Immunohistochemistry detected significant levels of only IREG1, which was localized to the basolateral membrane of colonic epithelial cells.
Iron absorption genes were expressed at lower levels in mouse caecum and colon than in the duodenum. They are regulated by body iron requirements. Colonic epithelial cells express basolateral IREG1in the same fashion as in the duodenum and this protein could regulate colonic epithelial cell iron levels.
据报道，大肠具有铁吸收能力，并表达十二指肠中常见的铁吸收基因。这些基因在大肠中的重要性和功能尚不清楚。因此，我们研究了这些基因在小鼠盲肠和结肠中的细胞定位及表达调控。
使用从缺铁和缺氧小鼠大肠中提取的RNA，通过实时PCR测定基因表达，并与对照组进行比较。使用同一小鼠大肠的冰冻切片，通过免疫组织化学测定蛋白质的定位和调控。
与十二指肠相比，Dcytb（十二指肠铁还原酶）在大肠中的表达水平非常低，而Ireg1和DMT1在大肠中表达水平显著，且在缺铁的盲肠、近端和远端结肠中表达增加，其中在远端结肠中增加最为显著。缺氧增加了近端结肠中Ireg1的表达。免疫组织化学仅检测到显著水平的IREG1，其定位于结肠上皮细胞的基底外侧膜。
铁吸收基因在小鼠盲肠和结肠中的表达水平低于十二指肠。它们受机体铁需求的调节。结肠上皮细胞以与十二指肠相同的方式表达基底外侧IREG1，该蛋白可能调节结肠上皮细胞的铁水平。
