Figure 6.

Specificity of binding to hepatoma estrogen binder. Fractions 33–35 were pooled from an experiment identical to that illustrated in Figure 5 except that the hepatoma cytosol was not labeled with [³H]E₂ before chromatography; instead, each fraction was tested for [³H]E₂ binding activity as indicated in Methods. The pooled fractions were tested for specificity by incubating with 5 nM [³H]E₂ in the absence or presence of a 100-fold excess of the potentially competing substance for 16 h at 0°C. In one experiment, the pooled fractions were labeled with [³H]E₂ as above, except that after incubation and dextran-coated charcoal treatment, the sample was treated with protamine sulfate and the supernatant estrogen binding activity was determined.