MCF-7 cells were treated for 24 hours with estradiol (1nM), EGF (150ng/ml; A, B), ATP (100uM; C), and calcium (5mM; D) in the presence and absence of the EGF receptor inhibitor AG1478 (1uM), the calcium chelator BAPTA (1uM), the antiestrogen ICI-182,780 (500nM), the PLC inhibitor U73122 (2 μM), or the intracellular calcium chelator BAPTA-AM (1uM). The amount of PgR and pS2 mRNA was measured using a real time RT-PCR assay and normalized to the amount of 18S ribosomal RNA for EGF and ATP treatments or GAPDH mRNA for calcium treatments. Data are expressed as percent control (mean±SD; three independent experiments). *, p < 0.05; **; p < 0.005; ***, p < 0.0005. a, compared to control; b, compared to treatment.