PSR mRNA levels in human lung microendothelial cells. (A) Time-dependent changes in PSR mRNA in HLMECs. Endothelial cells were incubated in the presence of IL-1α (10 ng per mL) for times indicated, and total RNA was isolated and analyzed for mRNA for PSR using a semiquantitative RT-PCR assay. (B) Effects of cytokines and heme on PSR mRNA expression in HLMECs. Endothelial cells were incubated for 4 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 mRNA. RT-PCR product of PSR mRNA from unactivated HT1080 cells (used as a positive control for PSR expression) is shown in lane 5 for comparison. β-Actin mRNA was coamplified with PSR mRNA as an endogenous control for quantitation. The RT-PCR products of PSR mRNA (372-bp band) and β-actin mRNA (687-bp band) from a representative experiment are shown. (C) Densitometric readings of the ratio between PSR and β-actin messages. Values, presented as fold-change relative to the corresponding media control, are the means (± SD) from 3 different experiments.