APStracts 2:0035G, 1995.

The role of nitric oxide in regulation of vascular resistance in postnatal intestine. Nowicki, Craig A. Nankervis Philip T. Department of Pediatrics, The Ohio State University and The Wexner Institute for Pediatric Research, Children's Hospital, Columbus, OH.

APStracts 2:0035G, 1995.

Studies were conducted to determine if endothelial production of nitric oxide (NO) participates in the regulation of vascular resistance in postnatal swine intestine. In vivo, intra-arterial infusion of the arginine analogue NG-monomethyl-L-arginine (LNMMA, 10-4M) increased intestinal vascular resistance 34% in 3- and 9% in 35-day old subject (p<.01); similar findings were noted during infusion of LNMMA at 10-3M. Mechanical augmentation of gut flow rate induced intestinal vasodilation in both age groups; LNMMA eliminated this flow induced dilation in 3-, but not in 35-day old intestine. In vitro, precontracted mesenteric artery rings from both age groups relaxed to a similar extent in response to endothelium-independent nitrovasodilator sodium nitroprusside (SNP) and the calcium ionophore A23187; the effect of A23187, but not SNP was eliminated by mechanical disruption of the endothelium. Acetylcholine (ACh) and substance P (SP), agents whose vascular effects are secondary to receptor-mediated activation of NO caused greater relaxation of rings from younger than older subjects and this effect was attenuated by LNMMA or methylene blue. Unstimulated accumulation of cGMP occurred to a similar extent in vessel segments from both groups. ACh and SP increased cGMP accumulation in segments from 3-, but not from 35-day old subjects. We conclude that the NO-cGMP axis participates to a greater extent in regulation of intestinal vascular resistance in 3- than in 35-day old swine.

Received 15 August 1994; accepted in final form 30 January 1995.
APS Manuscript Number G305-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 March 1995.