FIG. 1.

Effects of calcium channel blockers on β-cell TXNIP expression. A: INS-1 cells were incubated for 24 h with diltiazem (50 μmol/L), verapamil (50 μmol/L), NiCl₂ (500 μmol/L), or the calcium chelator EGTA (500 μmol/L), and TXNIP expression was assessed by quantitative RT-PCR. B: INS-1 cells were incubated for 48 h in the presence (V) or absence (C) of verapamil (50 μmol/L), and effects on TXNIP protein levels were assessed by Western blotting and corrected for β-actin. C: Isolated human islets were incubated for 24 h at the designated concentrations of verapamil, and TXNIP expression was assessed by quantitative RT-PCR. D: C57BL/6 mice received verapamil (100 mg/kg/day) in their drinking water for 3 weeks, and their islet TXNIP expression was assessed by quantitative RT-PCR. Bars represent means ± SEM of at least three independent experiments.