Figure 4. StAR is required for melatonin-induced P4 production in primary hGL cells. (A) Cells were treated with 500 μM melatonin for 24 h, and P4 levels in culture media examined using ELISA. (B) Cells were pre-treated with vehicle control (DMSO) or 10 μM LY294002 for 30 min and then exposed to 500 μM melatonin for 24 h. P4 levels in culture media were examined using ELISA. (C, D) Cells were transfected with 50 nM control siRNA (si-Ctrl) or StAR siRNA (si-StAR) for 48 h. (C) StAR siRNA knockdown efficiency was examined by western blot. (D) P4 levels in the culture media of si-Ctrl and si-StAR transfected hGL cells treated with 500 μM melatonin for 24 h were examined using ELISA. Results are expressed as the mean ± SEM of 4 independent experiments. Values without a common letter are significantly different (p < 0.05).