Suvarna S, McNabb F M, Dunnington E A, Siegel P B
Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg, 24061.
Gen Comp Endocrinol. 1993 Sep;91(3):259-66. doi: 10.1006/gcen.1993.1125.
Intestinal 5'deiodinase activity (5'D) in adults from lines of chickens selected for high (HW) and low (LW) juvenile body weight was studied in vitro using reverse T3 substrate. This avian intestinal 5'D activity is similar in its biochemical characteristics to the hepatic 5'D activity of mammals and birds. Adult 5'D activity was higher in line HW than LW; a pattern opposite to that prior to hatching. Previous studies have shown that thyroid hormones are important in triggering differentiation of the intestine during the latter part of embryonic life. Our studies indicate that the intestinal tissue is capable of producing T3 that may be important in stimulating differentiation of the intestine itself, in preparation for posthatching food assimilation. The intestines of LW embryos, which hatch earlier than HW embryos, show both more rapid maturation, as indicated by intestinal alkaline phosphatase activity (a marker of differentiation), and higher 5'D activity. Increases in intestinal 5'D in the HW line at hatch may be important in the differential intestinal growth that leads to higher relative intestinal weights in HW than LW chicks after hatch. The magnitude of 5'D activity and the relative size of the intestine suggest that this organ could be an important contributor to plasma T3.
利用反式三碘甲腺原氨酸底物，在体外研究了选择用于高（HW）和低（LW）幼年体重的品系成年鸡的肠道5'-脱碘酶活性（5'D）。这种禽类肠道5'D活性在生化特性上与哺乳动物和鸟类的肝脏5'D活性相似。成年鸡中，HW品系的5'D活性高于LW品系；这一模式与孵化前相反。先前的研究表明，甲状腺激素在胚胎后期触发肠道分化过程中很重要。我们的研究表明，肠道组织能够产生T3，这可能对刺激肠道自身分化很重要，为孵化后食物同化做准备。LW胚胎比HW胚胎孵化早，其肠道显示出更快的成熟，这通过肠道碱性磷酸酶活性（分化的标志物）和更高的5'D活性得以体现。孵化时HW品系肠道5'D的增加，对于导致孵化后HW雏鸡比LW雏鸡相对肠道重量更高的差异性肠道生长可能很重要。5'D活性的大小和肠道的相对大小表明，该器官可能是血浆T3的重要贡献者。
