Autoregulatory capacity in the superior mesenteric artery is
attenuated by nitric oxide.
Macedo, M. Paula, and W. Wayne Lautt.
LIVER RESEARCH UNIT, DEPARTMENT OF PHARMACOLOGY AND THERAPEUTICS,
FACULTY OF MEDICINE, UNIVERSITY OF MANITOBA, WINNIPEG, MANITOBA,
CANADA, R3E OW3, TELEPHONE: (204)789-3391, FAX: (204)783-6915
APStracts 3:0064G, 1996.
The hypothesis that nitric oxide antagonizes pressure-flow
autoregulation in the superior mesenteric artery was tested by the
use of a nitric oxide synthase inhibitor, N-nitro-L-arginine methyl
ester (L-NAME) and L-arginine. Autoregulation was assessed by the use
of two indices. 1) Autoregulatory index (ARI) expressed as the ratio
of change in flow to change in pressure tested over the non
-autoregulatory range, 40-70 mmHg, and over the autoregulatory range,
70-140 mmHg. 2) The slope index, which is an index of linearity of
the pressure-flow curve calculated by dividing the slope of the
pressure-flow curve over the autoregulatory range by the slope of the
non-autoregulatory range expressed as percent. L-NAME significantly
increased autoregulation from an ARI of 0.06 + 0.05 to 0.28 + 0.09
over the autoregulatory range (P<0.003) and the nitric oxide
synthase substrate, L-arginine reversed ARI to 0.12 + 0.07 (mean +
SE, n=7). ARI in the non-autoregulatory range was not altered. The
slope index revealed that L-NAME enhanced autoregulation (61 + 5.6
compared to control 93.4 + 7.9 (p<0.003)) which was partially
reversed by the action of L-arginine (88.5 + 5.5, p<0.007). The
data were consistent with the hypothesis that increased flow leads to
nitric oxide-induced dilation which counteracts autoregulation.
Received 25 September 1995; accepted in final form 12 March 1996.
APS Manuscript Number G420-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 1 April 96