Effect of PGE2 receptor inhibitors on PGE2-induced Egr2 mRNA expression. A, total RNA was extracted from UMR106 cells, and RT-PCR was used to amplify EP1, EP2, EP3, and EP4 receptor transcripts. B, UMR106 cells were seeded on 66-mm dishes and treated with exogenous PGE2 (5 μm) in the presence or absence of 30 μm AH6809 (EP1 and EP2 receptor antagonist). Total RNA was extracted 1 h after strain, and RT-qPCR was used to measure normalized Egr2 mRNA expression levels. Results are expressed as mean ± S.E. ***1, p < 0.001 versus vehicle; ***2, p < 0.001 versus PGE2. C, UMR106 cells were seeded on 66-mm dishes and treated with exogenous PGE2 in the presence or absence of 30 μm AH23848 (EP4 receptor antagonist). Total RNA was extracted 1 h after strain, and RT-qPCR used to measure normalized Egr2 mRNA expression levels. Results are expressed as mean ± S.E. *, p < 0.05 versus PGE2, ***, p < 0.001 versus vehicle, **, p = 0.01 versus strain.