Estrogen receptor expression analyzed by western blotting in placental types PT1–PT4 [PL in vivo; A] and corresponding early (TRC EC) and late trophoblast cultures (TRC LC) [B and C]. Samples are presented in the order they have been collected. [D] Cumulative data on ERα expression in normal (NP in vivo; n = 5) and abnormal placentae (AP in vivo; n = 5) and derived early (EC) and late cultures (LC). Different column superscripts indicate significant difference. Each column represents 30 measurements. Error bars = SD. Details in text.