EFFECTS OF NITRIC-OXIDE SYNTHESIS INHIBITION ON MESENTERIC PERFUSION IN YOUNG-PIGS

We tested the hypothesis that nitric oxide (NO) modulates postprandial hyperemia in young pigs. To test this hypothesis, we studied five gro ups of 3-wk-old pigs: group 1: milk fed, N-G-monomethyl-L-arginine (L- NMMA) and L-arginine (L-Arg) treated (n = 10); group 2: milk fed, plac ebo treated (n = 8); group 3: water fed, L-NMMA and L-Arg treated (n = 6); group 4: water fed, placebo treated (n = 4); and group 5: fasted sham fed, L-NMMA and L-Arg treated (n = 6). After catheter placement a nd electromagnetic flow probe instrumentation of the mesenteric artery systemic blood pressure and mesenteric artery blood flow were measure d during preprandial baseline, postprandial, and postprandial intra-ar terial L-NMMA- and L-Arg-infused study periods. The same measurements were made in the milk- and water-fed placebo-treated groups except tha t diluent replaced the L-NMMA and L-Arg infusions. In the milk- and wa ter-fed placebo-treated groups, a significant (analysis of variance, P < 0.05), postprandial hyperemia was observed. The change in blood flo w was greater (P < 0.05) in the milk-fed group a than in the water-fed group. Inhibition of NO synthesis with L-NMMA diminished (P < 0.05) t he hyperemic responses to both water and milk feeding and resulted in a decrease (P < 0.05) in mesenteric artery perfusion in the fasted sha m-fed state. We conclude that, in young pigs, NO is a modulator of mes enteric vascular tone in both the postprandial and fasted states.