Flow-mediated nitric oxide activity in the forearm vasculature of premenopausal women.

AIMS: Nitric oxide (NO) is involved in acute flow-mediated vasodilatation in various vascular beds. We determined whether acutely increasing flow in the human forearm of premenopausal women increases vascular NO activity. METHODS: Forearm blood flow (FBF) was measured by venous occlusion plethysmography. Responses to brachial artery infusion of noradrenaline (a control vasoconstrictor, 20, 50, and 100 ng min(-1), each for 5 min) and NG-monomethyl l-arginine (L-NMMA), an NO synthase inhibitor (200, 400, and 800 microg min(-1), each for 5 min), were determined in eight premenopausal women before and following elevation of basal FBF with glyceryl trinitrate (GTN) on two separate occasions. RESULTS: Flow elevation with GTN increased responses to L-NMMA (summary measure 103 +/- 12 vs 65 +/- 12 arbitrary units, P<0.05), but not to noradrenaline (95 +/- 35 vs 74 +/- 12, P=0.50). CONCLUSIONS: Acute elevation of FBF in nonpregnant women is associated with enhanced responses to NO synthase inhibition, consistent with flow-mediated increased NO activity.