Continued production of protein S by human vascular smooth muscle cells (HVSMCs) following extended periods of growth arrest.

HVSMC cultures at 90% confluency were placed in either control serum-free medium (C), medium containing vitamin K (1 μg/mL) (K), or warfarin (1 μg/mL) (W). Conditioned media were replaced every 3 days and were analyzed by Western blotting using a rabbit anti-protein S polyclonal antibody. pS represents 1 ng purified protein S.