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

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.

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.

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).

Acute elevation of FBF in nonpregnant women is associated with enhanced responses to NO synthase inhibition, consistent with flow-mediated increased NO activity.