Gastric mucosal blood flow in misoprostol pretreated aspirin-induced ulceration

To determine whether topical misoprostol (a synthetic PGE₁ analog) pretreatment will increase or prevent a decrease in gastric mucosal blood flow (GMBF) during topical aspirin administration, we studied focal GMBF simultaneously by hydrogen gas clearance in a split canine gastric chamber model with one side as control. In the test chamber, immediately after topical misoprostol, there was a transient and significant increase (18%) in GMBF (55.71 ± 7.80 to 65.84 ± 6.12 mL/min/100 g; p < 0.05). After 15 minutes, GMBF returned to premisoprostol levels and then showed a graded drop throughout the aspirin and postaspirin periods. No grossly visible mucosal lesions were observed. In the control chamber, mucosal lesions were observed 45 minutes after aspirin administration accompanied by a graded drop in GMBF throughout the experiments. Misoprostol neither produced a sustained increase in GMBF nor prevented the subsequent reduction in GMBF induced by aspirin. Therefore, maintenance of GMBF may not be important in cytoprotection by misoprostol. The sustained nonparietal secretion induced by this synthetic PGE₁ analog may be important in gastric cytoprotection.