Heid M K, Bills N D, Hinrichs S H, Clifford A J
Department of Nutrition, University of California, Davis 95616-8669.
J Nutr. 1992 Apr;122(4):888-94. doi: 10.1093/jn/122.4.888.
The incidence of neural tube defects was studied in mouse embryos from dams fed an amino acid-based diet containing 45, 91, 136, 181, 227 or 453 nmol folic acid/kg diet (Experiment 1) or 227, 453, 566, 680, 906, 1132, 1698 or 2266 nmol folic acid/kg diet (Experiment 2). Reproductive tracts were examined 12 d postcoitum and gross and microscopic examination of all embryos was performed. A single implantation was found at levels less than or equal to 181 nmol folic acid/kg diet. With one exception, bred mice fed 227 or 453 nmol folic acid/kg diet in Experiment 1 had 100% resorptions. In Experiment 2, 100% of implantations in mice fed 227 nmol folic acid/kg diet and approximately 75% of implantations in mice fed 453 or 566 nmol folic acid/kg diet resorbed. The 906 nmol folic acid/kg diet was sufficient for successful pregnancy. Mice fed 227 nmol folic acid/kg diet in Experiment 2 weighed approximately 80% of mice fed higher levels of folic acid. Inadequate dietary folic acid resulted in fewer and smaller embryos (which developed normally). These results suggest that folate deficiency alone is insufficient to produce neural tube defects in Swiss-Webster mice. Because individual micronutrients (e.g., folate) can be omitted from the amino acid-based diet, the specific role of folic acid in neurulation can now be studied systematically.
在喂食含45、91、136、181、227或453 nmol叶酸/千克日粮的氨基酸基日粮的母鼠所产小鼠胚胎中研究神经管缺陷的发生率（实验1），或在喂食含227、453、566、680、906、1132、1698或2266 nmol叶酸/千克日粮的母鼠所产小鼠胚胎中研究神经管缺陷的发生率（实验2）。在交配后12天检查生殖道，并对所有胚胎进行大体和显微镜检查。在叶酸水平小于或等于181 nmol/千克日粮时仅发现一次着床。除一个例外，实验1中喂食227或453 nmol叶酸/千克日粮的繁殖母鼠有100%的胚胎吸收。在实验2中，喂食227 nmol叶酸/千克日粮的小鼠中有100%的着床胚胎吸收，喂食453或566 nmol叶酸/千克日粮的小鼠中约75%的着床胚胎吸收。906 nmol叶酸/千克日粮足以成功怀孕。实验2中喂食227 nmol叶酸/千克日粮的小鼠体重约为喂食较高叶酸水平小鼠的80%。日粮叶酸不足导致胚胎数量减少且体积变小（胚胎发育正常）。这些结果表明，仅叶酸缺乏不足以在瑞士-韦伯斯特小鼠中产生神经管缺陷。由于氨基酸基日粮中可以省略个别微量营养素（如叶酸），现在可以系统地研究叶酸在神经胚形成中的具体作用。
