Protein fetal deposition

McCabe DP, Flynn EJ. 1990. Deposition of low dose benzo(a)pyrene into fetal tissue Influence of protein binding. Teratology 41(1) 85-95. 

Placental transport of lead may be associated with placental transport of calcium. Barltrop (1969) observed that femur lead increased rapidly in the third trimester, corresponding to onset of ossification and deposition of calcium. There is a question whether the increased deposition of lead in the femur along with calcium is because of some commonality between lead and calcium metabolism. Figure 2 shows the close correlation between size of fetal brain and increase in lead content as the brain matures. Whether the movement of lead into the brain is a matter of simple diffusion or whether there is some relationship to brain calcium is not known. Calcium deficiency does enhance lead absorption and the pathological effects of lead (Mahaffey et al. 1973). The placenta also contains a calcium-binding protein identical to that present in the intestine (Van Dijk 1981). A comparison of placental transfer of toxic metals by Nakano and Kurosa from the Minamata Institute in Japan (unpublished observation) found that lead levels in the placenta were strongly correlated with calcium, suggesting that lead deposition is associated with calcium deposition or with areas of dystrophic calcification that are present in the mature placenta. 

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