The effect of LE540, a specific antagonist for RARβ, on TM mRNA levels in the nuclei of HUVECs. HUVECs were incubated with or without 10 μM LE540 for 6, 12, or 24 hours. (A) TM mRNA levels in the cells were assayed by a quantitative RT-PCR method described in “Materials and methods.” The normalized signal is expressed as the percentage of control values (0 hours) after normalization to the β-actin mRNA signal. (B) TM antigen levels in cell lysate were determined by enzyme immunoassay. The data represent the mean ± SD from 4 independent experiments and are analyzed by the Student t test; *P < .05 when compared with control without LE540 (0 hours).