The role of prostaglandins in the rat gastric mucosal vascular response to acid stimulation was studied. Blood flow was measured with laser-Doppler flowmetry (LDF) and with red blood cell velocity measurements in the superficial mucosa; acid secretion was determined by titration. Baseline acid output was calculated to be 0.026 +/- 0.011 mueq/min. Pentagastrin (20 and 40 micrograms.kg-1.h-1 iv) significantly increased acid output to 0.387 +/- 0.104 and 0.546 +/- 0.220 mueq/min and LDF to 119 +/- 10 and 132 +/- 13% of control, respectively. LDF was significantly reduced by 15% after indomethacin (3 mg/kg iv) and was not changed by pentagastrin, whereas acid secretion increased to similar levels as without indomethacin pretreatment. The H2-agonist impromidine (100 and 500 micrograms.kg-1.h-1 iv) induced a dose-dependent increase in acid secretion (0.178 +/- 0.068 and 0.330 +/- 0.072 mueq/min, respectively) while blood flow was unchanged. Despite a substantial blood flow reduction (-38%) by indomethacin, impromidine did not alter blood flow, and acid secretion was dose dependently increased to similar values as without indomethacin pretreatment. These results provide further evidence that there is not necessarily any correlation between blood flow and acid secretion and that the pentagastrin-induced blood flow increase depends on prostaglandin release.