The −357 bp construct of the human type I InsP3 receptor gene promoter upstream of the CAT reporter gene in the pCAT-Basic plasmid was transiently transfected into G-292 osteosarcoma cells along with the pSV-β-galactosidase vector. In A, cells were treated for 48 h with or without 1 nm TPA, 10 nm 17β-estradiol, 10 nm 17α-estradiol, 100 nm tamoxifen, or the indicated combination. In B, cells were treated for 48 h with or without 10 nm 17β-estradiol, 20 nm ICI 182,780, or the combination. Extracts were normalized for β-galactosidase activities, and CAT activities were determined as described. The experiments are representative of two (A) and three (B) such experiments. Means ± S.E. for all experiments are reported under “Results.”