Placental maternal

Fig. 5.3.7 Disorders that affect the placental/maternal synthesis of estriol and diagnostic analytes for serum and urine. ORD Oxidoreductase deficiency, STS steroid sulfatase deficiency...

A bidirectional placental (maternal to fetal and fetal to maternal) transfer was described for instance by Thomas (1995). 

Data from a single study in dogs suggest that hepatic first-pass metabolism may limit systemic availability of the parent compound following oral exposure (Braeckman et al. 1983). Placental transfer of methyl parathion was demonstrated in pregnant rats 1-3 days before parturition. Thirty minutes after administration, both methyl parathion and methyl paraoxon were found in fetal brain, liver, and muscle methyl parathion, but not methyl paraoxon, was detected in placenta and maternal liver (Ackermann and Engst 1970). Methyl parathion binds reversibly to serum albumin, but is readily distributed to the tissues (Braeckman et al. 1980, 1983). 

Placental transfer of trichloroethylene occurs in animals. Trichloroethylene inhaled by pregnant sheep and goats, at levels used to induce analgesia and anesthesia, is rapidly distributed into the fetal circulation, with peak levels occurring approximately 40-50 minutes after maternal exposure (Helliwell and Hutton 1950). The concentration of trichloroethylene in umbilical vein blood was comparable to that found in the maternal carotid artery. 

Chasnoff, I.J. Schnol1, S.H. Burns, W.J. and Burns, K. Maternal nonnarcotic substance abuse during pregnancy Effects on infant development. Neurobehav Toxi col Teratol 6 277-280, 1984. Cooper, J.E. Cummings, A.J. and Jones, The placental transfer of phencyclidine in the pig Plasma levels in the sow and its piglets. J Phvsiol (Lond) 267 178-188, 1977. 

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. 

Ganapathy V, Prasad PD, Ganapathy ME, Leibach FH. Placental transporters relevant to drug distribution across the maternal-fetal interface. J Pharmacol Exp Ther 2000 294(2) 413-420. 

Timed-pregnant rats were dosed with l.Opg TCDD/kg on GD14. One day after birth, litters were cross-fostered to produce control, placental-only, lactational-only, and placental/lactational exposure groups. The DTH response to BSA was assessed in 5-month-old males. In these rats the severity of the suppression of the DTH response was related to the route of TCDD exposure (i.e., placental/lactational > lactational > placental), with suppression occurring only in the males receiving both placental and lactational exposure.128 In order to determine the lowest maternal dose of TCDD required to suppress the DTH response in pups, dams were dosed with 0.1,0.3, or l.Opg TCDD/kg on GD14 and the DTH response to BSA was evaluated in 4- and 14-month-old pups. In the males, suppression was observed at a maternal dose of O.lpg TCDD/kg at 14 months of age, while a maternal dose of 0.3pg TCDD/kg was required to cause suppression in... 

Montano, M.M. et al., Sex differences in plasma corticosterone in mouse fetuses are mediated by differential placental transport from the mother and eliminated by maternal adrenalectomy or stress, J. Reprod. Fertil., 99, 283, 1993. 

R.G. Richards, S.M. Hartman, and S. Handwerger. Human cytotrophoblast cells cultured in maternal serum progress to a differentiated syncytial phenotype expressing both human chorionic gonadotropin and human placental lactogen. Endocrinology. 135 321-329 (1994). 

Placental Barrier The placental barrier consists of several layers of cells between the maternal and fetal circulatory systems. Diffusion of polar drugs is limited. However, lipid-soluble drugs can pass through the barrier. Fetuses are rich in lipids and may form a reservoir for sequestering lipid-soluble drugs. 

---