FIGURE 7.

Beta cell Npas4 expression remains refractory for several hours after depolarization. MIN6 cells were stimulated for 2 h with 40 mm KCl (KCl) and transferred to basal medium for 1, 2, 3, or 5 h before restimulation with 40 mm KCl for 2 h. RNA was extracted and reverse-transcribed, and TaqMan PCR was carried out for Npas4 using GusB as a reference gene and normalizing to the initial 2-h KCl treatment. MIN6 cells remained refractory to KCl restimulation for up to 5 h before Npas4 induction, comparable with the initial KCl treatment. Error bars represent mean ± S.E., and significance was determined using a one-way ANOVA with Dunnett post hoc analysis (n = 4). *, p ≤ 0.05; **, p ≤ 0.01.