VITAMIN B12Co60 READILY PASSES THE PLACENTA INTO FETAL ORGANS AND NURSING PROVIDES B12 FROM MOTHER TO PUP

Abstract

The placenta is permeable to B12Co60. Together with salts, sugar, amino acids, vitamins, and proteins, the B12 is contributed to the growing embryos from the mother's body stores. At birth, the placenta contains a liberal amount of B12, which the mother regains by ingestion of the placentas. Nursing draws a liberal amount of B12Co60 from the mother's stores and contributes it to the body of the pups where it is absorbed and distributed in the various organs, much as noted when adult dogs are injected with B12Co60. A redistribution is noted as the months pass; but the high values in the heart, liver, and gastric mucosa persist, and the brain usually shows a slow increase. Enterohepatic circulation of B12 may involve bile and enteric content plus hepatic, gastric, and pancreatic epithelial secretion. This type of body recycling of radioactive B12 is discussed but not proven. High values of B12 in the heart, brain, gastric mucosa, and liver indicate that the vitamin is functionally active, not an inert fraction.

Time course of serum cobalamin, folate, and total iron binding capacity concentrations in pregnant bitches and association with hematological variables and survival

“…22 The etiology of the progressive decline in maternal serum cobalamin concentration during pregnancy is multifactorial. During fetal development, active cobalamin transport against a concentration gradient preferentially shunts cobalamin to the placenta and fetus, 17,[23][24][25] thereby depleting maternal reserves. 1 Cobalamin and folate tissue demand greatly increase during pregnancy in women, as reflected by elevated serum methylmalonic acid and homocysteine concentrations, even in face of normal cobalamin and folate concentrations.…”

Receptor-Mediated Endocytosis across Human Placenta: Emphasis on Megalin

“…The in vivo maternal–fetal PK studies of vitamin B12 (a megalin substrate) were also in agreement with those of AGs. Vitamin B12 was found to be transported readily across the placenta in animal models , as well as the human placenta . In rats which were intravenously dosed with 1–2 ng of radiolabeled vitamin B12 (specific activity 150 μCi/μg), there was retention of vitamin B12 in placental tissue for at least 2 h after administration, while there was no radioactivity in the fetal serum until 2 h after injection.…”