Explore of the regulatory factors involved in the nitrogen metabolic conversion in the ontogeny of amphibians

在两栖动物的变态过程中，肝脏开始合成尿素循环酶，这些酶是从二氧化碳和氨中产生尿素所必需的。我们探讨了氮代谢从排氨向排尿素转变的调控因子。氨甲酰磷酸合成酶1（CPS 1）mRNA的表达首次在st.47蝌蚪，表明早期蝌蚪产生和排泄尿素。我们检测了个体发育过程中糖皮质激素受体（GR）、CREB、HNF 3 α和C/EBPα mRNA表达的变化。结果表明，GR在st.44-45蝌蚪中的表达显著增加。我们还发现，皮质酮处理爪蟾蝌蚪（st. 44）CPS I mRNA的表达水平增加。因此，CPS I表达（尿素合成）在非洲爪蟾早期蝌蚪似乎是由皮质酮及其受体（GR）介导的。

During amphibian metamorphosis, the liver begins to synthesize the urea cycle enzymes necessary to create urea from carbon dioxide and ammonia. We explored the regulatory factor involved in a shift of nitrogen metabolism from ammonotelic to ureotelic. The expression of carbamoyl phosphate synthetase 1 （CPS1) mRNA was first detected at st.47 tadpoles, suggesting that early tadpole produces and excretes urea. We examined the mRNA expression changes in glucocorticoid receptor （GR), CREB, HNF3α, and C/EBPαduring ontogeny. In the results, GR expression was markedly increased in st.44-45 tadpole. We also revealed that corticosterone treatment for Xenopus tadpole （st.44) increased the expression level of CPS I mRNA. Accordingly, CPS I expression （urea synthesis) in early tadpole of Xenopus laevis appears to be mediated by corticosterone and its receptor （GR).