[Permeability of N,N-bis(2-chloroethyl)-diamido-phosphoric-acid into tumor cells (author's transl)]

The uptake of tritiated N,N-bis(2-chloroethyl)-diamido-phosphoric-acid into Ehrlich-Ascites-Tumor cells of mice was studied by means of the siliconoil-filtration technique. At 10 mM concentration no permeation of the metabolite into the tumor cells could be found within 5 min at 1 degrees C, while its congenors cyclophosphamide and 4-hydroperoxycyclophosphamide (1 mM) were shown to permeate into the cells very easily reaching saturation values. Thus lack of permeation into tumor cells of N,N-bis(2-chloroethyl)-diamidophosphoric-acid seems to be the reason for the poor cytotoxic activity of this metabolite of cyclophosphamide.