Levels in Human Placenta

Goyer and Cherian (1992) measured cadmium, zinc and copper, and metallothionein content of human placentas from 55 uncomplicated, full-term deliveries. The mothers ages ranged from 22 to 39 years, mean 29 years. All were current nonsmokers, but 16 (30%) acknowledged smoking in the past. None were on medication apart from iron and vitamin supplements. For 43 it was the first delivery, for 9 the second, for 1 the third, and for 2 the fourth. Samples of maternal and fetal blood were not obtained. Metals were measured by atomic absorption spectrophotometry and metallothionein by a silver saturation method (Scheuhammer and Cherian 1986). The results are shown in Table 1. Zinc levels of placentas were almost the same as those in the Kuhnert et al. (1988) study, but copper levels were considerably lower. No other comparable measurements of metallothionein were found in the literature. There is a strongly positive correlation between 

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Wibberlev DG, Khera AK, Edwards JH. et al. 1977. Lead levels in human placentae from normal and malformed births. J Med Genet 14 339-345. 

Wibberly, D. G., A. K. Khera, J. H. Edwards, et al. 1977. Lead Levels in Human Placentae from Normal and Malformed Births. Journal of Medical Genetics 14 339-345. 

Wibberly, D.G., Khera, A.K., Edwards, J.H. and Rushton, D.I. (1977). Lead levels in human placenta from normal and malformed births. ]. Med. Genet., 14, 339-345... 

Sokol, R.J., Martier, S. and Emhart, C.B. (1985). Identification of alcohol abuse in the prenatal clinic. In Early Identification of Alcohol Abuse. NIAAA Research Monograph-17, NIAAA Wesenberg, R.L. (1978). Neonatal thick blood" syndrome. Hosp. Pract., May, 137-145 Wibberley, D.G., Khera, A.K., Edwards, J.H. and Rushton, D.I. (1977). Lead levels in human placentae from normal and malformed births. ]. Med. Genet., 14, 339-345 Wirth, F.H., Goldberg, K.E. and Lubchenco, L.O. (1979). Neonatal hyperviscosity I. Incidence. Pediatrics, 63, 833-836... 

Bissonnette F, Cook C, Geoghegan T, et al. Transforming growth factor-alpha and epidermal growth factor messenger ribonucleic acid and protein levels in human placentas from early, mid, and late gestation. Am J Obstet Gynecol 1992 166 192-199. 

The OAT4 was cloned from human kidney but is also expressed at appreciable levels in the placenta (54). In kidney, OAT4 is localized to the apical... 

PFK-1 exists as a group of tissue-specific isoenzymes whose regulatory features match the role of glycolysis in different tissues. Three different types of PFK-1 isoenzyme subunits exist M (muscle), L (liver), and C. The three subunits show variable expression in different tissues, with some tissues having more than one type. For example, mature human muscle expresses only the M subunit, the liver expresses principally the L subunit, and erythrocytes express both the M and the L subunits. The C subunit is present in highest levels in platelets, placenta, kidney, and fibroblasts but is relatively common to most tissues. Both the M and L subunits are sensitive to AMP and ATP regulation, but the C subunits are much less so. Active PFK-1 is a tetramer, composed of four subunits. Within muscle, the M4 form predominates but within tissues that express multiple isoenzymes of PFK-1 heterotetramers can form that have full activity. 

Welsch, F., and Wenger, W. C. (1980). Acetylcholine in human placenta Identification by pyrolysis gas chromatography/ mass spectrometry and tissue levels following dilTerent modes of delivery. Naunyn-Schmiedherg s Arch. Pharmacol 311, 113-118. 

Epidemiological studies in humans have so far not shown any embryo-toxicity of cadmium. Traces of cadmium have been detected in aborted human material. In contrast to mercury and lead the concentrations of cadmium in human placentae are very high. This is demonstrated by Fig. 8, which was taken from a publication of Roels and coworkers (1978). These data show that the concentration of cadmium in the human placenta is nearly 10-times higher than cadmium concentrations in maternal and fetal blood. In further determinations cadmium concentrations in mother s milk were considerably lower than maternal blood levels. 

Bechi N, letta F, Romagnoli R et al (2010) Environmental levels of para-nonylphenol are able to affect cytokine secretion in human placenta. Environ Health Perspect 118(3) 427-431 Bennasroune A, Rojas L, Foucaud L et al (2012) Effects of 4-nonylphenol and/or diisononylphthalate on THP-1 cells impact of endocrine disrupters on human immune system parameters. Int J Immunopathol Pharmacol 25(2) 365-376 Bono-Blay F, Guart A, de la Fuente B et al (2012) Survey of phthalates, alkylphenols, bisphenol A and herbicides in Spanish source waters intended for bottling. Environ Sci Pollut Res Int 19(8) 3339-3349... 

Tissue-Specific Expression. In the adult rat, PPAR8 is expressed in all tissues examined, and often at levels higher than PPARa and PPARy. In human, PPAR8 is ubiquitously expressed, with higher expression in the digestive tract and placenta. 

There is no experimental evidence available to assess whether the toxicokinetics of -hexane differ between children and adults. Experiments in the rat model comparing kinetic parameters in weanling and mature animals after exposure to -hexane would be useful. These experiments should be designed to determine the concentration-time dependence (area under the curve) for blood levels of the neurotoxic /7-hcxane metabolite 2,5-hexanedione. w-Hcxanc and its metabolites cross the placenta in the rat (Bus et al. 1979) however, no preferential distribution to the fetus was observed. -Hexane has been detected, but not quantified, in human breast milk (Pellizzari et al. 1982), and a milk/blood partition coefficient of 2.10 has been determined experimentally in humans (Fisher et al. 1997). However, no pharmacokinetic experiments are available to confirm that -hexane or its metabolites are actually transferred to breast milk. Based on studies in humans, it appears unlikely that significant amounts of -hexane would be stored in human tissues at likely levels of exposure, so it is unlikely that maternal stores would be released upon pregnancy or lactation. A PBPK model is available for the transfer of M-hcxanc from milk to a nursing infant (Fisher et al. 1997) the model predicted that -hcxane intake by a nursing infant whose mother was exposed to 50 ppm at work would be well below the EPA advisory level for a 10-kg infant. However, this model cannot be validated without data on -hexane content in milk under known exposure conditions. 

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