DISPOSITION OF VITAMIN-K1 (PHYLLOQUINONE) IN THE ISOLATED PERFUSED HUMAN PLACENTAL LOBULE

The placental transfer of vitamin K1 was studied in isolation from maternal and foetal metabolism by using in vitro perfusion of an isolated human placental lobule. The disposition of [H-3]-vitamin K1 and [C-14]-antipyrine was investigated after dosing either maternal or foetal circulations and perfusing the isolated placental lobule in dual recirculating mode for 4 - 10 hours. The uptakes of [H-3]-vitamin K1 and [C-14]-antipyrine at maternal and foetal surfaces were compared after administering a single bolus dose. Although evidence was not found for significant transfer of vitamin K1 in either direction across the placenta the transfer of a small fraction of water-soluble tritium radioactivity was recorded. The observed uptake of vitamin K1 into placental tissue from maternal and foetal circulations of tissue culture medium (with or without added lipoprotein fractions), appeared to follow simple diffusion. However, while vitamin K1 was readily extracted into placental tissue form tissue culture medium (with or without added lipoprotein fractions), it was not readily extracted from maternal third-trimester serum and the existance of a specific transport mechanism for the transfer of vitamin K1 cannot be dismissed.