Fig. 5.
Characterization of concentration-dependent [Ca2+]e- and [Sr2+]e-mediated effects on cAMP formation in 6-23 cells. A, concentration-response curves of [Ca2+]e- and [Sr2+]e-mediated inhibition of forskolin-stimulated cAMP production. Responses are normalized to the cAMP production in response to 10 μM forskolin. B, concentration-response experiments of [Ca2+]e- and [Sr2+]e-stimulated cAMP production. The cAMP production in response to 10 μM forskolin is plotted as well as a positive control of AC activity. Concentration-response curves are representative of three independent experiments. C, modulation of 10 mM [Sr2+]e-mediated inhibition of forskolin-stimulated cAMP production (empty bars) by pertussis toxin and Calhex 231 and modulation of 100 nM octreotide-mediated inhibition of forskolin-stimulated cAMP production (filled bars) by pertussis toxin. Statistical comparisons of the values were performed by using a one-way ANOVA of each condition, and Dunnett's post-tests were used to compare 10 mM [Sr2+]e control response to the inhibition by pertussis toxin and Calhex 231. Statistical comparison of the responses to 100 nM octreotide and 100 nM octreotide + 100 ng/ml pertussis toxin was done by using Student's t test (n = 8). ***, p < 0.001.