Effect of warfarin on protein S secretion.

A. Human vascular smooth muscle cell (HVSMC) cultures at 90% confluency were incubated for 72 hours in control serum-free medium (C) or medium containing warfarin (1 μg/mL) (W) or vitamin K (1 μg/mL) (K). Conditioned media (CM) and cell lysates (CL) were analyzed by Western blotting using a rabbit anti-protein S antibody. B. HVSMC cultures at 90% confluency were incubated first for 72 hours with either control medium (C) or medium containing warfarin (1 μg/mL) (W); cells were then placed in new control medium (C) or medium containing vitamin K (10 μg/mL) (K), which was collected after 4 hours and analyzed by Western blotting using a rabbit anti-protein S antibody.