Figure 3.

Islet DNA strand breaks by alloxan (circles: upper panel) and streptozotocin (triangles: lower panel) (adapted from Ref. 4). Islets isolated from rat pancreas were incubated with alloxan or streptozotocin for 5–20 min in Krebs-Ringer’s bicarbonate medium. After incubation, DNA from islets that were laid for 10 min without the diabetogenic agents was recovered as a single peak near the bottom of the sucrose gradient, the position at which was undamaged DNA sediments. However, after only 5 min incubation with 1 mM of alloxan or 2 mM of streptozotocin, a considerable amount of DNA was deposited as a broad peak in the middle of the gradient with a concomitant decrease in undamaged DNA; after 10–20 min incubation, the DNA was almost completely fragmented. The effect of the two agents on islet DNA fragmentation was dose-dependent. These results indicate that alloxan and streptozotocin produce strand breaks in islet DNA.