Syncytiotrophoblasts placental

Although a uniform nomenclature for Na /H exchanger isoforms has not yet been adopted, we will refer to the amiloride-sensitive type of Na" /H exchanger that is present in the basolateral membrane of epithelia (apical membrane of placental syncytiotrophoblast) and also widely distributed in non-epithelial cells as the sensitive-type. The relatively amiloride-resistant isoform present in apical mem-... 

M. Inuyama, F. Ushigome, A. Emoto, N. Koyabu, S. Satoh, K. Tsukimori, H. Nakano, H. Ohtani, and Y. Sawada. Characteristics of L-lactic acid transport in basal membrane vesicles of human placental syncytiotrophoblast. Am J Physiol. 283 C822-C830 (2002). 

Estriol is also produced by another pathway in the syncytiotrophoblast cells of the placenta DHEAS from fetal adrenal is converted to 16a-hydroxydehydroepiandrosterone sulfate in the fetal liver, followed by removal of the sulfated chain to produce 16a-hydroxy-dehydroepiandrosterone, which is then aromatized to estriol. Estriol is the predominant estrogen produced during pregnancy, and almost all of tiie estriol and estradiol produced by the placental syncytiotrophoblast enters the maternal circulation. By the 7th week of gestation, the placenta produces the majority of the estrogen in the maternal circulation. 

Transendothelial IgG transport may be mediated by binding of endogenous IgG or exogenously administered monoclonal antibodies to FcyRIIa,b on endothelium (e.g., FcyRIIa on skin microvessels [27]) FcyRIIb on placenta villous (fetal) endothelium [28,29] or FcRn on placental syncytiotrophoblasts and fetal endothelium [28], Transcellular transport is further described below under FcRn-mediated transport, I cyRIIa-mediated transport, and specialized skin microvessel transport mechanisms. 

Kristoffersen EK, Matre R. Co-localization of beta 2-microglobulin and IgG in human placental syncytiotrophoblasts. Eur J Immunol 1996 26(2) 505-7. 

The placental fraction of alkaline phosphatase is a membrane-bound enzyme of 120 kD, normally synthesized by placental syncytiotrophoblasts and released into maternal circulation after the 12th week of pregnancy. However, it is also produced by many neoplasms and is a useful tumor marker. Physiologically, this enzyme is involved in cellular transport, proliferation and cellular differentiation, and regulation of metabolism and gene transcription. 

Johansson. M.. Jansson, T., Pestov, N. E., and Powell, T. L. (2004). Non-gastric H-i-ZK-l- ATPase is present in the microvillous membrane of the human placental syncytiotrophoblast. Placenta 25,505-511. 

Placental alkaline phosphatase (FLAP) Seminoma, embryonal carcinoma Proximal GIT tumors, lung and ovarian carcinoma Placental syncytiotrophoblasts... 

Dupressoir A, Vemochet C, Harper F, Guegan J, Dessen P, Pierron G, Heidmann T. A pair of co-opted retroviral envelope syncytin genes is required for formation of the two-layered murine placental syncytiotrophoblast. Proc Nad Acad Sci USA. 2011 108 El 164-73. doi 10.1073/pnas. 1112304108. 

BCRP (ABCG2) The breast cancer resistance protein (BCRP) transporter is also known as mitoxantrone resistance (MXR) protein (Miyake et al., 1999 Krishnamurthy and Schuetz, 2006). BCRP is expressed in plasma membrane of placental syncytiotrophoblasts of the chorionic villus (Mao, 2008 Robey et al., 2009), mammary glands, testis, canicular membrane of hepatocytes, cortical and proximal tubules in the kidney, villous tip of intestinal cells in the small intestine, hematopoietic stem cells, endothelial cells of venules and capillaries, and the luminal surface of the endothelial cells at the blood-brain barrier. The substrate specificity for BCRP overlaps broadly with P-gp therefore, the clinical DDI implications for BCRP are as yet not well defined. The current limited data suggest that BCRP may have an impact on chemoresistance in cancer (Noguchi et al., 2009). Rosuvastatin and topotecan have been reported to increase plasma AUC for antivirals and cyclosporins (Allen et al., 2002 Maliepaard et al., 2001, Table 4.8). 

Booth, A. G., Olaniyani, R. O, and Vanderpaye, O. A (1980) An improved method for the preparation of human placental syncytiotrophoblast microvilli. Placenta 1, 327-336. 

---