Fig. 7. Immunoblot analysis of insulin processing. Equal amounts of islet protein prepared from either wild-type (lanes 2 and 4) or oc/oc homozygous mice (lanes 3 and 5) were subjected to 15-25% gradient polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and 100 mM dithiothreitol. Human insulin was loaded as standard (lane 1). Immunoblotting was performed using anti-insulin or anti-C-peptide antibodies. The positions of a molecular weight marker are shown, and the positions of insulin and proinsulin are indicated (arrows). The intensities of the bands were measured using the image analyzer LAS1000. `Fold' indicates the ratio of the level of insulin over proinsulin in wild-type or mutant islets.