Fig. 5.

PGE₂ responses are desensitized following the 24-h pretreatment with an EP₂R-selective agonist but not by an EP₄R-selective agonist. a Acute cAMP responses in HFL-1 cells to various concentrations of PGE₂, ONO-AE1–259 (EP₂ agonist), or ONO-AE1–329 were measured. b HFL-1 cells were treated with 100 nM PGE₂, 100 nM ONO AE1–259 (EP₂ agonist), or 100 nM ONO-AE1–329 (EP₄ agonist) for 24 h then washed, and acute responses to PGE₂ were measured. cAMP levels were measured as a function of change in fluorescence normalized to the change in fluorescence of maximal response stimulated by 1 μM forskolin plus 200 μM IBMX using the cADDis assay. Data are mean ± SEM of n = 4. ONO-AE1–259 is not significant (p = 0.264), while ONO-AE1–329 is significant (p < 0.0001) from PGE₂ by 2-way ANOVA