Primary antibodies to ERα were purchased from Sigma-Aldrich (Merck); the antibodies against α-tubulin (Cell Signaling Technology) were added to standardize loading. Goat anti-rabbit IgGs (Jackson ImmunoResearch) conjugated to horseradish peroxidase were used as secondary antibodies. Signals were detected using the ECL reagent as described in Mruk and Cheng (2011) and an ImageQuant LAS4000 system (GE HealthCare). ImageJ software (NIH) was used for densitometry.