Cyclic AMP-Responsive Luciferase Assay in Mouse Leydig Cells

The MLTC-1 (mouse Leydig tumor cell–1) was obtained from the American Tissue and Cell Collection (ATCC, LGC Standards, Molsheim, France). Cell culture, plasmids and transfections were carried out according to the method described in our previous work [23 (link),30 (link)]. Cells were cultured at 37 °C and 5% CO₂ in RPMI-1640 medium (Gibco, Invitrogen, Saint-Herblain, France) supplemented with 10% fetal bovine serum, 50 µg/mL gentamicin, 10 units of penicillin/mL and 10 µg/mL streptomycin. Cells were transfected with pGlosensor-22F cyclic AMP plasmid using X-tremeGENE HP DNA transfection reagent. DNA (100 ng plasmid per well) and X-tremeGENE HP DNA transfection reagent (0.3 µL per well) were mixed together with serum-free RPMI medium and incubated at room temperature for 30 min. This plasmid consists in firefly luciferase sequence fused to that of the protein kinase A cyclic AMP-binding domain in a way that allows control of its enzymatic activity by cyclic AMP. And then the cells were sub-cultured at a density of 100,000 cells/well in 96-well plate (Dutscher, Brumath, France) overnight at 37 °C under 5% CO₂ before use of the cells in the assays.