Fig. 3.

Genetic degeneration of photoreceptors prevents diabetes-induced generation of superoxide in mouse retina. Photoreceptor degeneration was induced by genetic deficiency of opsin (opsin^−/−) in C57BL/6 mice. (A) Compared with wild-type control and diabetic mice, essentially all photoreceptors were missing from the retinas of opsin^−/− mice at 4 mo of age. ∆, N wild-type mice; ■, D wild-type mice; ▲, N opsin^−/−; □, D opsin^−/−. (B) The diabetes-induced increase in retinal superoxide production seen in wild-type mice was largely absent in diabetic mice lacking photoreceptors. Data are expressed as a percent of the value of nondiabetic wild-type controls. The duration of diabetes was 2 mo at the time of this assay (n = 3–5 per group).