Involvement of nitric oxide and prostaglandins in gastric mucosal hyperemia of portal-hypertensive anesthetized rats

This study investigates the effects of inhibition of nitric oxide synthesis by N^G-nitro-L-arginine methyl ester (L-NAME), the inhibition of prostaglandin synthesis with indomethacin and the combined effects on gastric mucosal hyperemia of ketamine-anesthetized rats with portal hypertension induced by partial portal vein ligation. The hydrogen gas–clearance technique was used for measurement of gastric mucosal blood flow. Blood pressure increased with L-NAME administration in a similar manner in portal-hypertensive and sham-operated rats. Low doses of L-NAME (1 and 3 mg/kg, intravenously) caused a significant and dosedependent reduction in gastric mucosal blood flow in portal-hypertensive rats but had no effect on shamoperated animals. With a higher dose of L-NAME (13 mg/kg, intravenously), a significant decrease in gastric mucosal blood flow was observed in both portal-hypertensive and sham-operated rats. Indomethacin pretreatment (5 mg/kg, subcutaneously) caused a significant decrease in basal gastric mucosal blood flow of portal-hypertensive rats but did not modify this parameter in sham-operated animals. In sham-operated rats pretreated with indomethacin, the lower dose of L-NAME (3 mg/kg) did not significantly modify basal gastric mucosal blood flow. Likewise, pretreatment with indomethacin in sham-operated rats did not augment the significant reduction in gastric mucosal blood flow produced by the higher dose of L-NAME. In portal-hypertensive rats the significant dose-dependent reduction in gastric mucosal blood flow induced by L-NAME (3 and 13 mg/kg) was not significantly altered by pretreatment with indomethacin. Portal pressure was higher in portal-hypertensive than in sham-operated rats, and no significant differences were observed in this parameter between portal-hypertensive animals treated with different doses of L-NAME. These results indicate that both nitric oxide and prostaglandins may be involved in the gastric mucosal hyperemia of portal-hypertensive rats. However, no synergistic interactions between these two endogenous vasodilators could be observed in this experimental model. (HEPATOLOGY 1993;18:628–634.)