FIGURE 7.

Mouse islet glucose competence is modulated by IGF-1R and IGF-2 expression. A, mouse islets were infected with a control adenovirus (Ad GFP) or an IGF-1R-expressing adenovirus (AdIGF1-R) and 2 days later exposed to either 2 or 20 mm glucose, and insulin secretion was measured and expressed as in Fig. 6. B, mouse islets were infected as in A and 2 days later exposed to either 2 or 20 mm glucose in the presence of a control IgG or an IGF-2 blocking antibody. Insulin secretion is reported relative to secretion at 2 mm glucose (stimulatory index). C, mouse islets were infected with an adenovirus expressing a unrelated (Luc) or an IGF-2-specific shRNA, and the islets were then processed as above for measurement of glucose-stimulated insulin secretion. The Western blot in the right panel shows the reduction in ProIGF-2 expression in AdshIGF-2-infected cells. IGF-1R, IGF-2, and β-actin expression was detected by Western blot analysis. The data are the means ± S.D. from three independent experiments. *, p < 0.05; **, p < 0.01; ***, p < 0.001.