VASOCONSTRICTOR SENSITIVITY TO NORADRENALINE AND N-G-MONOMETHYL-L-ARGININE IN MEN AND WOMEN

1, Nitric oxide has potential anti-atherogenic actions as well as regu lating vascular tone, Animal studies suggest that there are sex differ ences in basal nitric oxide biosynthesis, but it is not known whether such differences exist between men and women, 2, We have investigated this question by measuring forearm blood flow responses, using venous occlusion plethysmography, to brachial artery infusion of NG-monomethy l-L-arginine (an inhibitor of NO biosynthesis) and noradrenaline in 40 healthy subjects (20 men and 20 premenopausal women), Mean arterial b lood pressure was 89 +/- 10 mmHg (mean +/- SD) in men and 87 +/- 9 mmH g in women, and mean total cholesterol was 4.25 +/- 0.99 mmol/l (mean +/- SD) and 4.26 +/- 0.80 mmol/l respectively, 3, In men, vasoconstric tor responses to N-G-mono-methyl-L-arginine, 1-4 mu mol/min (15-28% me an reduction in blood flow), were consistently less than responses to noradrenaline, 60-240 pmol/min (26-37%), whereas in women, vasoconstri ctor responses to NG-monomethyl-L-arginine (19-30%) were consistently greater than those to noradrenaline(11-17%). The sex difference in rel ative sensitivity to vasoconstrictors was significant (P < 0.001), 4, Our findings are consistent with either greater sensitivity to noradre naline in men compared with premenopausal women, or a greater basal ni tric oxide biosynthesis in premenopausal women compared with men.