Riboflavin uptake in microvillous and basal membrane vesicles isolated from full-term human placentas.
Riboflavin uptake was characterized using membrane vesicles isolated from the apical (maternal-facing) and basal (fetal-facing) membranes of the syncytiotrophoblast from full-term human placentas. Equilibrium [3H]riboflavin uptake was insensitive to variations in incubation medium osmolarity in contrast to [3H]alanine uptake into an osmotically sensitive space. Osmotic insensitivity suggested riboflavin binding to a membrane component. The dissociation constant of riboflavin binding was similar in microvillous (Kd = 2 microM) and basal membrane vesicles (Kd = 1 microM). Binding capacity was significantly higher in microvillous membranes (Bmax = 11.9 pmol/mg protein). The relatively high affinity binding to the membrane vesicles may represent a first step in riboflavin transport.
Moe
A J
AJ
Edward Mallinckrodt Department of Pediatrics, Children's Hospital, Washington University School of Medicine, St Louis, MO 63110.
Plas
D R
DR
Powell
K A
KA
Smith
C H
CH
D000409:Alanine / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D006801:Humans; D007700:Kinetics; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D009994:Osmolar Concentration; D010206:Papain / Q000494:pharmacology; D010920:Placenta / Q000648:ultrastructure*; D011247:Pregnancy; D012256:Riboflavin / Q000378:metabolism*; D014316:Tritium; D014327:Trophoblasts / Q000648:ultrastructure
D014316:Tritium; D010206:Papain; D000409:Alanine; D012256:Riboflavin