INHIBITORS OF THE PLASMA-MEMBRANE REDOX SYSTEM OF ZEA-MAYS L ROOTS - THE VITAMIN-K ANTAGONISTS DICUMAROL AND WARFARIN

The action of the 4-hydroxycoumarins dicumarol and warfarin, antagonists of probable vitamin K type components of the plasma membrane electron-transport system, on plasma membrane redox activity of intact maize roots was compared. Both effectors inhibited electron transfer to extracellular hexacyanoferrate III. While the effect of the strongly lipophilic dicumarol on the electron-transport system was irreversible by rinsing, the inhibition caused by the hydrophilic warfarin could be reverted completely by exchange of the incubation medium. We take these results as possible evidence for the integration of dicumarol into the plasma membrane. The action of warfarin may be confined to enzymic sites freely accessible from the aqueous apoplasmic solution.