4,5-Diaminofluorescein (DAF-2) is a newly developed indicator of nitric oxide (NO). Two amino groups of DAF-2 are oxidized by NO. We investigated the effects of reducers on the NO-induced oxidation of DAF-2. NOC-5 (0.1-10 microM), a NO-donor, concentration-dependently elicited fluorescence with 10 microM DAF-2. The rate of the fluorescence reaction was dependent on the width of the excitation band path. The presence of catecholamines (1 microM), but not tyrosine or phenylephrine, attenuated the fluorescence induced by NOC-5. Ascorbate and other reducers like dithiothreitol, 2-mercaptoethanol, or glutathione (all 1 mM) abolished the fluorescence. These results suggest that reducers attenuate the NO-induced fluorescence of DAF-2 mainly through an anti-oxidative action.

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Objectives: Digital refractory gangrene is rarely found in collagen diseases, including systemic sclerosis and is possibly caused by similar underlying vascular damage in peripheral arterial disease (PAD) such as arteriosclerosis obliterans (ASO) and/or thromboangiitis obliterans (TAO) by unclarified mechanisms other than vasculitis and thrombosis. This study evaluated the radiological imaging in patients with digital gangrene associated with collagen disease and compared the images with those of PAD based on the results of laboratory and histopathological examinations. Methods: Angiography, MR angiography and/or CT angiography were performed on 6 patients with refractory gangrene or extensive ulcers accompanied by scleroderma-spectrum disorders; 3 with diffuse systemic sclerosis, 1 with limited systemic sclerosis, 1 with overlap syndrome and 1 with Sjögren's syndrome. Results: Although the vascular alterations in collagen diseases were similar to those in PAD, the abnormal image findings (occlusion or stenosis of the arteries with smooth vessel walls) found in collagen diseases did not include atheromatous plaque, which are worm-like vessels that are characteristic of those observed in PAD. Conclusions: Some cases of digital gangrene seen in collagen diseases show similar vascular imaging patterns to those of PAD and comprehensive examinations including arterial imaging can be useful for the diagnosis of these unrecognized vascular changes other than vasculitis or digital thrombosis.