Fig. 1.
IL-1 induces β-cell death and rat islet degeneration in a nitric oxide-dependent manner. A: rat islets (150 islets/400 μl CMRL) were incubated with IL-1 (10 U/ml) ± ng-monomethyl-l-arginine (l-NMMA) (2 mM) for 48 h. Cell viability was determined using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. The culture supernatants were harvested for nitrite determination. B: rat islets (150 islets/400 μl CMRL) were treated with IL-1 (10 U/ml) ± l-NMMA (2 mM) for 4 or 7 days as indicated. B, lower middle and bottom: effects of the addition of l-NMMA 24 (bottom left) or 36 h (bottom right) after IL-1, followed by continued culture with IL-1 and l-NMMA for a total of 96 h. Islet morphology was examined by phase contrast microscopy. Note that the islet shown in B, bottom right (IL-1 + l-NMMA added at 36 h), is representative of the few healthy islets observed at this time point. The majority of the islets have degenerated into clusters of 100–200 cells (IL-1 at 4 days; upper middle left, inset). Results are the average ± SE of 3 independent experiments (A) or representative of 3 experiments (B). Statistically significant increases in cell death and nitrite production are indicated (*P < 0.05).