Placenta function

The placenta functions as a barrier between fetus and mother329-331. The elemental content of the placenta provides an indication of the nutritional/excretory maintenance of the pregnancy. The concentrations of elements in placental tissue are at low pg-1-ng g-1 levels and multi-element precise methods, including INAA, were applied to determine more than forty elements in this tissue332 333. The average contents of silver and gold [given in pg g-1 (dry wt)] in 100 hospitalized deliveries were found to be [Ag] = 0.0049 0.0014 and [Au] = 0.00024 0.00010. These two metals are neither essential trace metals nor are they toxic. 

The placenta functions as a barrier between fetus and mother . The elemental content of the placenta provides an indication of the nutritional/excretory maintenance of the pregnancy. The concentrations of elements in placental tissue are at low... 

Hydroxy vitamin D pools ia the blood and is transported on DBF to the kidney, where further hydroxylation takes place at C-1 or C-24 ia response to calcium levels. l-Hydroxylation occurs primarily ia the kidney mitochondria and is cataly2ed by a mixed-function monooxygenase with a specific cytochrome P-450 (52,179,180). 1 a- and 24-Hydroxylation of 25-hydroxycholecalciferol has also been shown to take place ia the placenta of pregnant mammals and ia bone cells, as well as ia the epidermis. Low phosphate levels also stimulate 1,25-dihydtoxycholecalciferol production, which ia turn stimulates intestinal calcium as well as phosphoms absorption. It also mobilizes these minerals from bone and decreases their kidney excretion. Together with PTH, calcitriol also stimulates renal reabsorption of the calcium and phosphoms by the proximal tubules (51,141,181—183). 

TRPV5 and TRPV6, also known as the epithelial Ca2+ channel or ECaC (TRPV5) and Ca2+transporter 1 or Ca2+ transporter-like (TRPV6), are the only two Ca2+-selective TRP channels identified so far. They may function in vitamin D-dependent transcellular transport of Ca2+in kidney, intestine and placenta. TRPV6 is also expressed in pancreatic acinar cells, and in prostate cancer, but not in healthy prostate or in benign prostate hyperplasia. 

Ilback NG, Sundberg J, Oskarsson A. 1991. Methyl mercury exposure via placenta and milk impahs natural killer (NK) cell function in newborn rats. Toxicol Left 58 149-158. 

Lead concentrations in maternal and umbilical cord blood have been reported by Greek researchers for 50 parturient women at delivery. Twenty-five of the women lived in industrial areas with high air pollution, and twenty-five lived in agricultural areas with low air pollution. The mean lead concentrations (expressed as mean standard deviation) for the women living in areas with high air pollution were 37.2 4.7 pg/L in maternal blood and 20 3.4 pg/L in umbilical cord blood (correlation coefficient, r = 0.57). The mean lead concentrations for the women living in areas with low air pollution were 20.5 5.6 pg/L in maternal blood and 12.9 3.6 pg/L in umbilical cord blood (correlation coefficient, r = 0.70). The authors conclude that the placenta demonstrates a dynamic protective function that is amplified when maternal PbB levels are raised (Vasilios et al. 1997). 

Kekuda, R., et al. Cloning and functional characterization of a potential-sensitive, polyspecific organic cation transporter (OCT3) most abundantly expressed in placenta. J. Biol. Chem. 1998, 273, 15971-15979. 

Wu, X., et al. Structural and functional characteristics and tissue distribution pattern of rat OCTN1, an organic cation transporter, cloned from placenta. Biochim. Biophys. Acta 2000, 1466, 315-327. 

Within the OAT family, OAT4 is the only transporter expressed at appreciable levels in both the placenta and in the kidney [54]. The membrane localization of OAT4 within these tissues has not been examined. Steroid sulfates, and ochratoxinA are efficient transport substrates of OAT4, whereas PAH is weakly transported [54]. The functional importance of OAT4 in regulating placental permeability and renal drug elimination is currently unknown. 

Normal spleen lymphocyte function Maximum nickel concentrations in tissues (in mg/kg FW) were reached in blood (19.8) and placentas (3.9) 2 h following injection those in liver (4.9), spleen (1.3), and kidneys (56.2) were reached 4 h after injection and maximum concentration in fetal tissues (1.1) was reached after 8 h. Authors estimate that all nickel is excreted in 42 to 84 h Immunosuppression in spleen lymphocyte function LD50 (48 h)... 

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