Hemorrhage- and resuscitation-related alterations in gastrointestinal circulation: effect of a low dose of L-NMMA.

The gastrointestinal tract, including its mucosal barrier, is most sensitive to ischemic insults. The present study was conducted to evaluate hemorrhage- and resuscitation-related regional alterations in gastrointestinal circulation in presence or absence of a low dose of N(G)-monomethyl-L-arginine (L-NMMA), a nonspecific nitric oxide synthase inhibitor. Organ-specific circulation was studied using the colored microsphere technique in rats subjected to prolonged hemorrhagic shock (180 min) followed by resuscitation with or without L-NMMA (2 mg/kg body weight) treatment at the end of resuscitation. We found an initial distal gradient in the intestinal blood flow with the highest rate in duodenum followed by jejunum, ileum, and colon. Hemorrhage resulted in the highest decrease in gastric blood flow. Resuscitation restored circulation in the intestinal tract to baseline levels except for gastric blood flow. L-NMMA treatment after completion of resuscitation did not deteriorate gastrointestinal blood flow. Our data show (a) a distal gradient in the intestinal blood flow from duodenum to colon, (b) that hemorrhage and resuscitation cause different degrees of alteration in gastric and intestinal blood flow, (c) that gastric perfusion does not recover after resuscitation, predisposing to further organ damage, and (d) that a low dose of L-NMMA does not deteriorate intestinal circulation in rats subjected to hemorrhage and resuscitation.