Different numbers of MCF-7 cells enriched for membrane estrogen receptor-α (mER) and MCF-7 cells depleted for membrane estrogen receptor-α (mER; 1000–7000/well) were plated, fixed with 2% paraformaldehyde/0.1% glutaraldehyde, and then quantified via the CV assay at 590 nm absorbance. Different numbers of mERcells were assessed in parallel with CV and MTT assays to demonstrate a linear correlation between these assays. The values are means for 28 samples ± standard error.