Carbenoxolone disodium salt (CBX; Sigma) was used as a gap junction inhibitor. Human connexin-32 plasmid (Cx32), C-terminally tagged with mEmerald, was obtained from Addgene (plasmid #54054) [48 (link)] while pcDNA 3.1 mock plasmid was purchased from Invitrogen. EVOS fluorescent microscope was used to verify the expression of Cx32 in cells (Additional file 3 : Figure S3). Co-cultures of GS-293 and FSHR-293 cells were transiently transfected with Cx32 plasmid to determine the effect of connexin overexpression on cAMP transfer.
For determining cell viability after CBX treatment, co-cultures of GS-293 and FSHR-293 were preincubated with different concentrations of CBX (25, 50, 75 and 100 μM) for 2h in assay medium. Assay medium was then discarded, followed by washing with PBS. Cell viability was then assessed by CellTiter AQueous non-radioactive cell proliferation assay (Promega) following manufacturer’s instructions. Briefly, cells were incubated in DMEM complete medium (without phenol red) containing MTS/PMS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium/phenazine methosulfate] solution for 2h (37°C, 5% CO2). Absorbance was then read at 490 nm, which provides a measure of cellular viability. One-way analysis of variance (ANOVA) was used to determine statistical differences among different samples.
For determining cell viability after CBX treatment, co-cultures of GS-293 and FSHR-293 were preincubated with different concentrations of CBX (25, 50, 75 and 100 μM) for 2h in assay medium. Assay medium was then discarded, followed by washing with PBS. Cell viability was then assessed by CellTiter AQueous non-radioactive cell proliferation assay (Promega) following manufacturer’s instructions. Briefly, cells were incubated in DMEM complete medium (without phenol red) containing MTS/PMS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium/phenazine methosulfate] solution for 2h (37°C, 5% CO2). Absorbance was then read at 490 nm, which provides a measure of cellular viability. One-way analysis of variance (ANOVA) was used to determine statistical differences among different samples.