Abstract：
The oviduct of the Chinese brown frog (Rana dybowskii) expands during pre-brumation rather than the breeding period, exhibiting a special physiological feature. Vitamin A is essential for the proper growth and development of many organisms, including the reproductive system such as ovary and oviduct. Vitamin A is metabolized into retinoic acid, which is crucial for oviduct formation. This study examined the relationship between oviducal expansion and vitamin A metabolism. We observed a significant increase in the weight and diameter of the oviduct in Rana dybowskii during pre-brumation. Vitamin A and its active metabolite, retinoic acid, notably increased during pre-brumation. The mRNA levels of retinol binding protein 4 (rbp4) and its receptor stra6 gene, involved in vitamin A transport, were elevated during pre-brumation compared to the breeding period. In the vitamin A metabolic pathway, the mRNA expression level of retinoic acid synthase aldh1a2 decreased significantly during pre-brumation, while the mRNA levels of retinoic acid α receptor (rarα) and the retinoic acid catabolic enzyme cyp26a1 increased significantly during pre-brumation, but not during the breeding period. Immunohistochemical results showed that Rbp4, Stra6, Aldh1a2, Rarα, and Cyp26a1 were expressed in ampulla region of the oviduct. Western blot results indicated that Aldh1a2 expression was lower, while Rbp4, Stra6, RARα, and Cyp26a1 were higher during pre-brumation compared to the breeding period. Transcriptome analyses further identified differential genes in the oviduct and found enrichment of differential genes in the vitamin A metabolism pathway, providing evidences for our study. These results suggest that the vitamin A metabolic pathway is more active during pre-brumation compared to the breeding period, and retinoic acid may regulate pre-brumation oviductal expansion through Rarα-mediated autocrine/paracrine modulation.
摘要：
中国褐蛙（Ranadybowskii）的输卵管在繁殖前而不是繁殖期间扩张，表现出特殊的生理特征。维生素A对许多生物体的正常生长和发育至关重要，包括生殖系统，如卵巢和输卵管。维生素A被代谢成维甲酸,这对输卵管形成至关重要。这项研究检查了输卵管扩张与维生素A代谢之间的关系。我们观察到在预冲洗期间，Ranadybowskii的输卵管重量和直径显着增加。维生素A及其活性代谢产物,视黄酸,在预消毒期间显着增加。视黄醇结合蛋白4(rbp4)及其受体stra6基因的mRNA水平,参与维生素A的运输，与繁殖期相比，在预繁殖期间升高。在维生素A代谢途径中，维甲酸合成酶aldh1a2的mRNA表达水平在预处理期间显著下降，而维甲酸α受体（rarα）和维甲酸分解代谢酶cyp26a1的mRNA水平在预复制期间显着增加，但不是在繁殖期间。免疫组化结果显示,Rbp4、Stra6、Aldh1a2、Rarα、Cyp26a1在输卵管壶腹区域表达。Westernblot结果显示Aldh1a2表达较低,而Rbp4，Stra6，RARα，与繁殖期相比，Cyp26a1在预繁殖期间更高。转录组分析进一步确定了输卵管中的差异基因，并发现了维生素A代谢途径中差异基因的富集，为我们的研究提供证据。这些结果表明，与繁殖期相比，维生素A代谢途径在预繁殖期间更加活跃，视黄酸可能通过Rarα介导的自分泌/旁分泌调节来调节血管扩张。
