['Human vascular endothelial cells express the estrogen receptor-beta (ER-beta), which can be modulated by the opiate alkaloid morphine.', 'To determine if morphine is capable of down regulating the ER-beta receptor in a similar fashion as the mu opiate receptor since they are both coupled to constitutive nitric oxide synthase derived nitric oxide release.', 'Endothelial cells obtain from human vascular tissues (saphenous vein, atria and primary saphenous vein cells) were treated with 1 uM morphine plus or minus the mu opiate receptor antagonist naloxone or CTOP (10 uM) for 24 h at 37 degrees C. Total RNA was isolated from treated and untreated primary endothelial cells, and specific primers and a probe were used to determine the ER-beta gene expression by real-time RT-PCR. Cells treated with morphine exhibited a down-regulation of ER-beta, whereas naloxone and CTOP were able to partially block the morphine effect. In addition, the 266 bp fragment generated by RT-PCR using the same primers as in the real-time PCR was sequenced and revealed a 100% sequence identity as the authentic ER-beta gene sequence.'] Does morphine down regulate human vascular tissue estrogen receptor expression determined by real-time RT-PCR?