PSR protein expression by human lung microendothelial cells. (A) Time-dependent expression of PSR protein in HLMECs. Endothelial cells were incubated in the presence of IL-1α (10 ng per mL) for times indicated, and total proteins were isolated and analyzed for PSR protein using Western blots as described. (B) Effects of cytokines and heme on PSR protein expression in HLMECs. Endothelial cells were incubated for 6 hours in the absence (lane 1) or presence of 10 ng/mL IL-1α (lane 2), 10 ng/mL TNF-α (lane 3), or 100 μM heme (lane 4) and then analyzed for PSR protein. Total protein extract from unactivated HT1080 cells (used as a positive control for PSR protein expression) is shown in lane 5 for comparison. Equal protein loading was checked by reprobing the stripped immunoblots for β-tubulin protein. PSR and β-tubulin protein bands from a representative immunoblasts are shown. Vertical lines between lanes have been inserted to indicate repositioned gel lanes. (C) Densitometric readings of the ratio between PSR and β-tubulin proteins: Values are the means (± SD) from 3 different experiments.