Fig 4.

Intracellular and extracellular cAMP levels in P3HR-1, Akata, BCBL-1, and JSC-1 cells. Cells were cultured for 24, 72, or 120 h in the presence or absence of the inducing agent (TPA or IgG), and cAMP levels were measured by ELISA. The intracellular cAMP levels represent the amount of cAMP in 10⁶ cells, and the extracellular levels are expressed as the amount of cAMP in 1 ml of medium containing 10⁶ cells. Each bar represents the mean ± standard error of the mean of at least two independent experiments. **, P < 0.01; ***, P < 0.001.