Rat pancreatic β cells exhibit a 16-fold higher glutamate decarboxylase (GAD) activity than islet non-β cells, but a similar glutamate dehydrogenase (GDH) activity, β Cells which survive exposure to 2 mM streptozotocin only contain 10 percent of the GAD activity of control cells, but their GDH activity remains unaltered. Culture of streptozotocin-treated β cell preparations with 2 mM nicotinamide reduces the number of dead cells and prevents in part the decline in GAD activity of surviving β cells. These data indicate that loss in activity of the β cell specific enzyme GAD can serve as marker for β cells which survived a destructive process. It is furthermore demonstrated that nicotinamide increases the percent surviving cells and decreases their loss in GAD activity.
