Objective: To investigate the mechanism by which over-dose retinoic acid inhibits cardiogenesis in Xenopus laevis. Methods-. The embryos at stage 14 were cultured with retinoic acid (1×10-6 mol/L). Four hours later, the embryos were used for whole mount in situ hybridization for Tbx20. Explants from embryos of Xenopus laevis at stage 14 were isolated for culture with retinoic acid (1× 10-6 mol/L) and BMP. Four hours later, RNA transcripts were examined through whole mount in situ hybridization for Tbx20. Results-. (1) Excess retinoic acid significantly inhibited Tbx20 expression in the early heart; (2) BMP blocked inhibitory effects of retinoic acid on Tbx20 transcription. Conclusion-. Retinoic acid inhibits cardiogenesis in Xenopus laevis by decreasing Tbx20 expression.%目的:研究过量视黄酸抑制爪蟾早期心形成的机制.方法:用过量视黄酸培养发育到第14期的胚胎.4h后,胚胎用MEMPHA固定进行转录因子Tbx20的胚胎整体原位杂交.取发育第14期胚胎形成心的组织,并分别加入视黄酸和骨形成蛋白进行培养.4h时后,用MEMPHA固定并进行Tbx20的胚胎整体原位杂交.结果:视黄酸降低Tbx20在早期心组织中的表达；在早期心组织中骨形成蛋白阻止了视黄酸对Tbx20表达的抑制作用.结论:过量视黄酸通过降低Tbx20的表达,抑制了爪蟾心的形成.
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