Nitric oxide mediated vasodilation in human pregnancy. Williams, David J, Patrick Jt Vallance, Guy H Neild, John Ad Spencer, Fred J Imms. Departments of Nephrology, Clinical Pharmacology and Obstetrics and Gynaecology, University College London Medical School, London, UK; and Sherrington School of Physiology, UMDS (St Thomas's Campus)' London, UK
APStracts 3:0360H, 1996.
The maternal circulation vasodilates during pregnancy. We investigated the contribution of nitric oxide to this vasodilatation. Using venous occlusion plethysmography we measured the effect of nitric oxide synthase inhibition on hand blood flow during human pregnancy. We compared the response to a brachial artery infusion of the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) with the response to noradrenaline in three groups of women; non-pregnant, early pregnant (9-15 weeks) and late pregnant (36-41 weeks). Basal hand blood flow increased significantly during late pregnancy compared with non-pregnant and early pregnant subjects (p=0.007). L -NMMA produced a greater reduction in hand blood flow in both pregnant groups compared with non-pregnant controls (p=0.0003). Noradrenaline produced an attenuated response in late pregnancy compared to non -pregnant and early pregnant women (p=0.0029). If other vascular beds respond in the same way as the hand, the gestational increase in vasoconstrictor response to L-NMMA that we observed, implicates increased generation of nitric oxide in the fall of peripheral vascular resistance during healthy human pregnancy. 

Received 17 April 1996; accepted in final form 14 August 1996.
APS Manuscript Number H345-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996