Nitric oxide regulates endothelium-dependent vasodilator responses
in the rabbit hindquarters vascular bed in vivo.
Cohen, Gordon A., Adrian J. Hobbs, Richard M. Fitch, Michael J.
Zinner, Gautam Chaudhuri, and Louis J. Ignarro.
Departments of Pharmacology, Surgery, and Obstetrics and
Gynecology, UCLA School of Medicine, 10833 Le Conte Avenue, Los
Angeles, California 90024
APStracts 2:0531H, 1995.
The objective of this study was to determine whether nitric oxide (NO)
could function as a negative feedback modulator of endothelium -
dependent vasodilation in vivo. To this end, the influence of
exogenous NO on vasodilator responses in the rabbit hindquarters
vascular bed was determined. Previous in vitro studies have
demonstrated that NO inhibits both neuronal NO synthase from rat
cerebellum as well as NO synthase derived from bovine aortic
endothelial cells. The present study was conducted in the rabbit
hindquarters vascular bed under conditions of constant blood flow so
that changes in pressure directly reflected changes in vascular
resistance. Under these in vivo conditions, the NO-donor agent S
-nitroso-N-acetylpenicillamine (SNAP) reversibly attenuated responses
to the endothelium - dependent vasodilator, acetylcholine and
bradykinin. In contrast, SNAP did not influence the endothelium -
independent vasodilator response to SNAP itself or to 8-Br-cGMP.
These observations indicate clearly that NO interferes with
endothelium - dependent vasodilator action and supports the view that
endogenous NO may actually play a physiological role in regulating
vascular tone.
Received 8 June 1995; accepted in final form 16 November 1995.
APS Manuscript Number H524-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 December 95