Figure 4.

Effect of alloxan and streptozotocin on pancreatic islets (adapted from Ref. 4). Nuclear fraction from islets was incubated in conditions causing breaks in islet DNA, and PARP activity was assayed (Upper). Both streptozotocin (2 mM) and alloxan (1 mM) induced a 2- to 3-fold increase in PARP activity, with a peak at 10 min. Cellular NAD⁺ content was reduced by either 2 mM streptozotocin or 1 mM alloxan within 20 min of incubation and remained almost unaltered for 60 min (Lower). There was a striking temporal correlation between the decrease in the level of islet NAD⁺ and the increase in islet PARP activity.