PC-12 cells are a chromaffin-like tumor cell line of adrenal origin, that undergoes neuronal differentiation in response to nerve growth factor. In pilot experiments we observed that exposure of PC-12 cells to diabetic serum resulted in cell death. The aims of this study was to determine if cell death was via apoptosis and evaluate the role of nitric oxide. Exposure of PC-12 cells to diabetic serum derived from strepotozotocin treated rats, caused time and concentration dependent cell death. After incubation for 24 hr with 7.5% diabetic serum, cell count was 64±36% of baseline whereas with control serum cell count was 142±29% of baseline (p<0.01). Cell death was complete at 48 hr with diabetic serum concentration of 7.5% and above. Apoptosis, as determined morphologically, positive TUNEL immunohistochemical staining and cell death ELISA assay, was the mechanism of cell death. Coincident with apoptotic cell death was the expression of inducible nitric oxide synthase (determined by immunohistochemistry) and elevated media nitrite levels. 10±1.7 μM of nitrite compared to the control value of 3±1.2 μM (p<0.05). However, incubation with the nitric oxide synthase inhibitors, L-NMMA or L-NIL (0.1 - 1.0mM), or dexamethasone, did not modify diabetic serum-induced cell death. Thus while inducible nitric oxide synthase is associated with PC-12 cell death it is not a critical mediator of apoptosis in response to diabetic serum. These findings suggest that apoptosis and nitric oxide may contribute to the manifestations of clinical diabetic neuropathy.