Objective: To measure skin blood flow responses to the iontophoresis of acetylcholine and sodium nitroprusside in the digits of patients with systemic sclerosis (SSc) and control subjects. Additionally, to test the effects of oral L-arginine supplementation versus placebo in patients.
Methods: Skin blood flow was measured at the dorsum of the finger using laser Doppler flowmetry during iontophoresis of endothelium dependent (acetylcholine) and independent (sodium nitroprusside) vasodilators. L-arginine and placebo supplementation were given in a double blind, crossover fashion (8 g daily for 28 days).
Results: In comparison to control subjects, dose dependent vascular responses to acetylcholine were diminished in patients with SSc (1.7 +/- 0.3, 3.6 +/- 0.7, 5.9 +/- 1.5 vs 1.4 +/- 0.1, 2.4 +/- 0.6, 2.4 /- 0.5; p < 0.01, ANOVA). Vascular responses to sodium nitroprusside were not significantly different between control subjects and SSc patients. L-arginine supplementation, however, had no significant effect on vascular responses to acetylcholine and sodium nitroprusside.
Conclusion: There is an abnormality of endothelial dependent vasodilatation in the digital vasculature of patients with SSc. The lack of effect of supplementation with L-arginine suggests the abnormality may be independent of the L-arginine/nitric oxide pathway and may involve prostanoids.