title: Establishment of gradients of riboflavin, L-lysine and alpha-aminoisobutyric acid across the perfused human placenta.
abstract: The mechanism for establishing transplacental gradients was studied in the dually perfused human placental lobule by recirculating either the maternal or fetal perfusate and leaving the other circuit open. Antipyrine, used as a reference molecule, rapidly reached equivalent concentrations in both perfusates regardless of which was recirculated. In contrast, riboflavin, L-lysine and alpha-aminoisobutyric acid showed distinctive kinetics at each surface of the placenta. Recirculation of the maternal perfusate quickly depressed the concentrations of these compounds and maintained them at levels of 50-70% of the fetal concentration. Recirculation of the fetal perfusate was followed by a gradual increase in concentrations, establishing gradients 1.2-1.7 times the maternal. It appears that uptake at the maternal surface greatly exceeds release, whereas the two rates are more nearly balanced at the fetal surface. The net effect is extraction of substrate from the maternal circulation and transfer to the fetal, where it accumulates to form a gradient.
mesh_terms: D000621:Aminoisobutyric Acids / Q000378:metabolism*; D000983:Antipyrine / Q000378:metabolism; D005260:Female; D006801:Humans; D008239:Lysine / Q000378:metabolism*; D008431:Maternal-Fetal Exchange; D010477:Perfusion; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D012256:Riboflavin / Q000378:metabolism*
chemical_list: D000621:Aminoisobutyric Acids; C100049:2-aminoisobutyric acid; D008239:Lysine; D000983:Antipyrine; D012256:Riboflavin