Figure 3.

Progestin-induced cell proliferation is dependent on MAPK and independent of cPR. A, BrdU chemiluminescence ELISA was carried out to determine the signaling cascade of progestin-induced cell proliferation. Rat NPCs were starved for 4 h before exposure to 100 pm progestin alone or progestin combined with MAPK inhibitor UO126 (100 nm) for 24 h, and cell proliferation was evaluated by BrdU chemiluminescence ELISA measuring BrdU incorporation. Ethanol + DMSO (1 × e⁻⁶) was used as vehicle control, and bFGF was used as positive control. Data were collected from four independent assays, analyzed using one-way ANOVA, followed by Neuman-Keuls post hoc test, and plotted as percentage increase vs. vehicle control (mean ± sem). *, P < 0.05; **, P < 0.01; ***, P < 0.005; and ****, P < 0.0001 vs. vehicle control; †, P < 0.05; ††††, P < 0.001 vs. progestin-alone group. B, Structure-activity analysis of progestin-induced proliferative effects. Critical structural features of progestins required for proliferative effects from SAR analysis.