RegI and RegII levels in the pancreas of young and old WT and PARP-1−/− mice before and after low-dose STZ treatment. (A) Double staining for insulin (green) and RegI (red) or (B) stained with RegII (red) and counterstained with DAPI (blue) (n = 4–5). Bar = 50 µm. (C) Quantitative analysis of RegI protein expressed as fold increase over the control group (young WT mice before low-dose STZ treatment) (n = 5). *p < 0.05 versus old WT mice (control group). **p < 0.01 versus old WT mice (STZ group). (D) Quantitative analysis of RegII protein expressed as fold increase over control group (young WT mice before a low-dose STZ treatment) (n = 5). **p < 0.01 versus old WT mice.