Endothelial and adrenergic dysfunction in Raynaud's phenomenon and scleroderma

Objective. To investigate the involvement of endothelial and adrenergic mechanisms in patients with Raynaud's phenomenon (RP) and scleroderma. Methods. Ten patients with RP and scleroderma and 10 healthy volunteer controls were studied. Intraarterial methacholine, sodium nitroprusside, and clonidine were administered while bilateral finger blood flow was measured with venous occlusion plethysmography. Results. Compared to the controls, the patients showed diminished responses to methacholine, an endothelium dependent vasodilator, and to clonidine, an α₂-adrenergic agonist. However, both groups showed similar responses to sodium nitroprusside, an endothelium independent vasodilator. Conclusion. The findings were consistent with previous histological evidence of endothelial damage in scleroderma blood vessels. Failure to release nitric oxide from vascular endothelium may play a role in RP in patients with scleroderma.