Placental Transfer

The placenta: a multifaceted, transient organ

“…Both are active in the syncytiotrophoblast of the human placenta [30,31]. During the first trimester, a number of proteins of maternal origin accumulate in the coelomic and amniotic fluids [32], whereas later in pregnancy, immunoglobulin G (IgG) crosses the placenta by this mechanism [24]. Specificity and the ability to avoid lysosomal degradation during the endocytosis phase may be provided by the presence of receptors for IgG in the microvillous membrane invaginations and vesicles.…”

“…Transporter proteins form a large and diverse family, but share common features such as substrate specificity, saturation kinetics and the ability to be competitively inhibited [24]. Transporter proteins may allow exchange down a concentration gradient at a faster rate than simple diffusion alone, often referred to as facilitated diffusion.…”

Placental nutrient supply and fetal growth

“…Consequently, with reference to the Fick equation described above, the diffusional transfer of these substances is much less affected by concentration gradients (and therefore by blood flow unless this is very low) and is more affected by the surface area of the barrier available for diffusion and the thickness of this barrier. The S.Dw/l term in the Fick equation is conveniently described and measured as a permeability x surface area product (P.S) in studies of diffusional permability of the placenta to hydrophilic molecules (Atkinson et al, 2006;Sibley and Boyd, 1988). P.S has been measured in vitro and in vivo in a number of different species (Atkinson et al, 2006;Sibley and Boyd, 1988) and two important facts have emerged.…”

“…The S.Dw/l term in the Fick equation is conveniently described and measured as a permeability x surface area product (P.S) in studies of diffusional permability of the placenta to hydrophilic molecules (Atkinson et al, 2006;Sibley and Boyd, 1988). P.S has been measured in vitro and in vivo in a number of different species (Atkinson et al, 2006;Sibley and Boyd, 1988) and two important facts have emerged. Firstly, P.S is inversely proportional to the radius of inert hydrophilic solutes of increasing molecular size.…”

“…Placental transfer has been the focus of many reviews which document the various transport pathways in detail (Atkinson et al, 2006;Boyd et al, 1994;Morriss et al, 1994;Sibley and Boyd, 2004;Smith et al, 1992). These pathways include those mediated by diffusion and those utilizing transcellular mechanisms, mediated by transporter proteins in the plasma membranes, as discussed in the following sections.…”