Figure 2.

Glucose toxicity activates the PERK and IRE1α arms of the UPR pathway. (a) Quantitative RT-PCR of wild-type C57BL/6 islets cultured for 1 to 3 days either in a control medium or in a medium containing 50 mM ribose. Relative mRNA expression levels for Chop, Atf4, Bip, Pdia4, P58 and XBP1-unspliced/spliced were calculated by normalizing to the signal for β-Actin mRNA in each sample and comparison with islets cultured in a control medium. Results represent mean±s.e.m. of n=3–6 independent experiments. *P<0.05, ***P<0.001 when comparing islets cultured in ribose with those cultured in a control medium (one-way ANOVA). (b) Eight hundred wild-type C57BL/6 islets were cultured in a control medium or in a medium containing 50 mM ribose. Positive control islets were cultured in 5 μm thapsigargin. Western blotting was performed with antibodies to CHOP (31 kDa), BiP (78 kDa) and β-Actin (45 kDa) (loading control). Results are representative of three independent experiments