Effect of P4 and MPA on expression of decidual products. A) St-T1b cells were incubated in MM1 for 9 days as outlined in the scheme. Cultures were stimulated for 3 or 7 d with 8-Br-cAMP (0.5 mM) alone or in combination with P4 or MPA (1 μM). Supernatants were collected from the last 3 days of treatment, and RNA was harvested. B) RT-PCR analysis was performed for the indicated products on cells that had been stimulated for 3 or 7 d. C) Supernatants of the cultures described above, stimulated for 3 or 7 d, were assayed for IGFBP-1. Values represent IGFBP-1 secretion over 3 d, normalized to total RNA content of the wells. Means ± SD are shown (n = 3 wells). ANOVA followed by Bonferroni's post-hoc test revealed significant differences (**, P < 0.01; ***, P < 0.001; s, significantly different from controls, P4 and MPA after 3 and 7 d with P < 0.001; ns, not significantly different from controls, P4 or MPA after 3 and 7 d).