Figure 5.

CHA-mediated inhibition of cyclic AMP formation. The figure shows the ability of CHA to inhibit the formation of cyclic AMP induced by 1 μM forskolin in TSH-deprived control cells with an IC₅₀ of 2.05 nM and in cells constantly grown with 0.3 mu ml⁻¹ TSH with an IC₅₀ of 0.14 nM. Forskolin induced a 525% increase in cellular cyclic AMP in TSH-deprived cells and a 425% increase in cells constantly grown with TSH. The basal values were 6.4 pmol per 10⁶ cells and 7.7 pmol per 10⁶ cells, respectively. Data are mean±s.e.mean from five separate experiments.