Responses to stable ectopic estrogen receptor-beta expression in a rat fibroblast cell line

To examine activity of estrogen receptor-beta (ER beta) independently of estrogen receptor-alpha (ER alpha), retrovirus-mediated gene transfer was used to insert rat ER beta into a rat fibroblast cell line (rat-1) that does not ordinarily express ER. Stable expression of ER beta in rat-1 cells was validated and then characterized by reverse-transcription polymerase chain-reaction (RT-PCR) analysis to examine the effects of estradiol (E-2) treatment on expression of specific target mRNAs. Results were compared with rat-1 cells and a previously constructed rat-1 + ER alpha cell line. Progesterone receptor mRNA was not detected in rat-1 cells and was induced by E-2 in both rat-1 + ER alpha and rat-1 + ER beta cells. Treatment with E-2 resulted in an increased rate of cell proliferation (P < 0.05) in rat-1 + ER alpha cells, but not in rat-1 or rat-1 + ER beta cells. Data confirm studies using transient ER expression demonstrating that ER alpha and ER beta have both discrete and overlapping activity within the same cell type in the presence of the same ligand. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.