Fig. 1. H₂O₂ suppresses PTH-stimulated cAMP formation and ERK activation.

A) HEK-293R cells were transiently transfected with an EPAC FRET sensor to measure cAMP. After a 60-sec baseline recording 100 nM NNT-PTH in PBS was added and recording continued for an additional 5 min. Pretreatment with 100 μM H₂O₂ for 15 min decreased cAMP formation. Data are the mean ± SEM of N = 3 independent experiments with n = 20 (PTH[1-34] or 30 (H₂O₂ + PTH[1-34]). B) pERK1/2 activation was similarly measured using the ERK-NES FRET sensor. Here, a 2-min baseline recording was followed by introduction of 100 nM NNT-PTH. 100 μM H₂O₂ for 15 min decreased pERK1/2. Data are the mean ± SEM of N = 3 independent experiments with n = 22 (PTH[1-34] or 15 (H₂O₂ + PTH[1-34]).