[The transport mechanism of antibiotics using microvillous membrane vesicles (placental transport of fosfomycin)].

Using the rapid filtration technique, the uptake of fosfomycin into microvillous membrane vesicles isolated from human term placental trophoblast was investigated. The microvillous membrane vesicles exhibited the uptake of fosfomycin into an osmotically reactive intravesicular space and it was indicated that the uptake of fosfomycin by microvillous membrane vesicles represented transport into membrane vesicles. The uptake of fosfomycin by microvillous membrane vesicles was not dependent on the Na+ electrochemical gradient or membrane potential. The initial uptake of fosfomycin by microvillous membrane vesicles did not exhibit saturation kinetics with respect to fosfomycin concentration, and increased linearly as the fosfomycin concentration increased. These results indicated that fosfomycin was transported across the microvillous membrane by simple diffusion. L-alanine, L-valine, L-lysine, inorganic phosphate or D-glucose did not inhibit the uptake of fosfomycin into microvillous membrane vesicles. On the other hand, fosfomycin did not inhibit the uptake of L-alanine, L-valine, L-lysine inorganic phosphate or D-glucose into microvillous membrane vesicles. These results revealed that fosfomycin did not affect the placental transport activity of other nutrients.