Cadmium placental transfer

Lauwerys R, Buchet J-P, Roels HA, et al. 1978. Placental transfer of lead, mercury, cadmium, and carbon monoxide in women I. Comparison of the frequency distributions of the biological indices in maternal and umbilical cord blood. Environ Res 15 278-289. 

Cadmium does not readily pass the blood-brain barrier, the blood-testis barrier or the placental barrier, but it accumulates in the placenta of animals and humans [14]. In humans, placental transfer of Cd seems to be very low and Cd is found to accumulate in the placenta [15,16]. 

Eisenmann CJ, Miller RK. 1994. The placental transfer and toxicity of selenite relative to cadmium in the human term perfused placenta. Placenta 15 883-985. 

Kelman (1979) has studied the placental transfer of cadmium in guinea pigs. In this species the placental membranes are not at all limiting the transfer of cadmium to the embryo. According to this investigator the low concentrations of cadmium that are usually found in the embryo are due to the extremely rapid distribution in the maternal compartments which is quite different from the situation for both mercury and lead. 

Roels H, Hubermont G, Buchet JP, Lauwerys R (1978) Placental transfer of lead, mercury, cadmium, and carbon monoxide in women. III. Factors influencing the accumulation of heavy metals in the placenta and the relationship between metal concentration in the placenta and in maternal and cord blood. Environ. Res. 16 236 Wilson JG (1973) Environment and birth defects. Academic Press, New York - London Wilson JG (1977) Current status in teratology - general principles and mechanisms derived from animal studies. In Handbook of teratology, Vol. 1, eds. Wilson JG, Fraser FC, Plenum Press, New York, p. 75... 

Sonawane BR, Nordberg M, Nordberg GF, Lucier GW (1975) Placental transfer of cadmium in rats influence of dose and gestational age. Environ Health Perspect 12 97-102... 

The purpose of this chapter is provide an overview of the mechanisms for transport of two toxic metals, lead and cadmium, and to identify factors that may influence this process. The mechanisms for transfer of these two metals differ in that lead is readily diffusible across the placenta. There is no placental barrier for lead, whereas the placenta provides a protective barrier to fetal exposure to cadmium. Consideration of the placental transport of these two metals is prefaced by a few comments on possible experimental... 

Placental metallothionein binds zinc and copper as well as cadmium. Zinc and copper are essential nutrients for the fetus whereas cadmium is toxic to the fetus and retained rather than transferred to the fetus. There is a question, therefore, as to how the essential metals are preferentially transported to the fetus while the toxic metal, cadmium, is retained. One possibility is that there is a greater sensitivity for zinc and copper metallothionein than cadmium metallothionein to the action of proteolytic enzymes present in trophoblasts. Degradation of the zinc and copper metallothionein complex facilitates the release of these metals to fetal blood, whereas cadmium metallothionein is resistant to this effect. 

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