EFFECTS OF ENDOTHELIUM-DERIVED NITRIC-OXIDE ON SKIN AND DIGITAL BLOOD-FLOW IN HUMANS

The effects of N-G-monomethyl-L-arginine (L-NMMA) on total finger and forearm, and dorsal finger and forearm skin, blood flows were studied in the basal state and during reflex sympathetic vasoconstriction in n ormal subjects. Total flows were measured by venous occlusion plethysm ography and skin flows by laser-Doppler flowmetry (LDF). L-NMMA in dos es of 2, 4, and 8 mu M/min given by constant infusion via a brachial a rtery catheter significantly decreased finger blood flow, forearm bloo d flow, and vascular conductances. At 8 mu M/min, total finger blood f low decreased 38.4% and forearm blood flow decreased 24.8%. Dorsal fin ger and forearm skin LDF were also significantly decreased (25 and 37% at 8 mu M/min). Body cooling significantly decreased finger blood flo w (73.6%), vascular conductance, and finger LDF (59.7%). L-NMMA had no effect on total finger blood flow or dorsal finger LDF during body co oling. Nitric oxide or related compounds contribute to the basal dilat or tone of the dorsal finger and forearm skin but not during reflex sy mpathetic vasoconstriction.