Muir M, Landon M
Br J Haematol. 1985 Oct;61(2):303-6. doi: 10.1111/j.1365-2141.1985.tb02829.x.
The cobalamin content of placenta, maternal and fetal sera was assayed by methods which measure microbiologically-active and microbiologically-inactive cobalamins. Only microbiologically-active cobalamins were present in the placenta but both types were present in both maternal and fetal circulations. We conclude that only microbiologically-active cobalamins cross the placenta and that the microbiologically inactive cobalamins in the fetus must arise by metabolism in situ.
采用能测定微生物活性钴胺素和微生物非活性钴胺素的方法，对胎盘、母体血清和胎儿血清中的钴胺素含量进行了测定。胎盘内仅存在微生物活性钴胺素，而母体和胎儿循环中两种类型的钴胺素均有存在。我们得出结论，只有微生物活性钴胺素能穿过胎盘，胎儿体内的微生物非活性钴胺素必定是由原位代谢产生的。
