Protease signaling in endothelial cells from Par1^–/–:Par2^–/– mice. Dermal microvascular endothelial cells isolated from Par1^–/–:Par2^–/– neonates or matched controls were serum-starved, loaded with ³H-inositol, and exposed to vehicle, protease, or agonist peptide as indicated. To exclude nonspecific responses to contaminating thrombin, hirudin was included with all proteases except thrombin. Results from 2 independent experiments are shown. Each bar represents 1 experiment done in triplicate; error bars show standard deviation. Par1^–/–:Par2^–/– cells did respond to nonprotease agonists such as serum and lysophosphatidic acid; h indicates human; m, mouse.