Increase in cAMP enhances inter-TEC GJIC. Panels A and B depict untreated co-cultures of the mouse TEC line at zero and 6 hours time points, respectively. The percentage of double positive cells and the calcein geometric mean fluorescence intensity (MFI) of these populations are depicted at the upper right corner of each panel (%, above; MFI, below). Panels C and D show the inter-TEC coupling, following 6 hours of treatment with 1 mM 8-Br-cAMP or 10 μM forskolin. Both treatments enhanced the calcein mean fluorescence intensity of coupled cells (double positive cells). These data are representative of at least 4 separate experiments. Such enhancements can also be seen in Panels E to H, depicting TEC co-cultures treated for 6 hours with increasing concentrations of either 8-Br-cAMP (E-F) or forskolin (G-H). While percentages of coupled TEC was not significantly modified (E, G), the geometric mean fluorescence of calcein quantified from the double positive cells tripled after both treatments (F, H). The results are representative of 3 independent experiments (mean SD). Panel I shows that 8-Br-cAMP was also capable of enhancing inter-TEC GJIC, in primary cultures of human TNC-derived epithelial cells. Numbers of coupled cells were count in blind. * p < 0.05.