Figure 5
17β-Estradiol (E2) dose-dependent cAMP responses and proliferation in MCF-7 cells enriched for membrane estrogen receptor-α (mERhigh; closed circles) versus MCF-7 cells depleted for membrane estrogen receptor-α (mERlow; open circles). (a) cAMP response; each experiment was repeated three times with triplicate samples, and the data were approximated with a four-parameters Gaussian equation. The two sets of data were compared by evaluating the differences between the sums of squares of the residuals from each individual curve with the sum of squares of the residuals of the combined curve using the F-test. The curves were significantly different (P = 0.02). (b) E2 dose-dependent proliferation curves vary with mER expression level. mERhigh cells (closed circles) exhibited a biphasic growth pattern, whereas mERlow cells (open circles) responded with a sigmoid growth pattern. The cells were treated on separate plates with different concentrations of E2 or ethanol vehicle (0.1%) for 5 days. The data are percentages of control, and expressed as mean values ± standard error from three separate experiments, each containing 40 replicates.