t-Butyl hydroperoxide can activate the tissue factor pathway involving new synthesized protein induced by native LDL; oxidized LDL lipid extracts can activate surface tissue factor without new protein synthesis.

(A) Rat aortic smooth muscle cells were treated without or with LDL (200 μg protein/mL). Two hours later t-butyl hydroperoxide (25 μg/mL) was added to the wells of the groups indicated. After an additional 2 hours, surface tissue factor activity was assayed in all wells. (B) Total lipid extracts of oxidized LDL, at a concentration equivalent to 200 μg protein/mL of intact lipoprotein were added to rat aortic smooth muscle cell layers. Some were treated with cycloheximide (20 μmol/L; filled bars) 30 minutes before, and concurrent with lipid treatment. Tissue factor pathway activity was measured after 2 hours of lipid treatment. Data represent means ± SD of 4 wells per treatment.