THE ACTIONS OF NITRIC-OXIDE DONORS IN THE PREVENTION OR INDUCTION OF INJURY TO THE RAT GASTRIC-MUCOSA

1 The protective or damaging actions on the gastric mucosa, of locally infused nitrovasodilators that donate nitric oxide (NO), have been investigated in the pentobarbitone-anaesthetized rat. 2 Local intra-arterial infusion of endothelin-1 (ET-1; 5 pmol kg-1 min-1 for 10 min) induced extensive, macroscopically apparent, haemorrhagic injury to the rat gastric mucosa. This damage was dose-dependently reduced by concurrent local intra-arterial infusion of glyceryl trinitrate (GTN; 10-40 mug kg-1 min-1) which liberates NO on metabolic transformation, or the nitrosothiol, S-nitroso-N-acetyl-penicillamine (SNAP, 2.5-10 mug kg-1 min-1) which spontaneously liberates NO. 3 Local infusion of higher doses of SNAP (20 and 40 mug kg-1 min-1. i.a.) did not, however, significantly protect against mucosal injury induced by ET-1. 4 Furthermore, local infusion alone of these higher doses of SNAP, as well as sodium nitroprusside (10-40 mug kg-1 min-1, i.a.) which also spontaneously liberates NO, induced significant mucosal injury, as assessed macroscopically and confirmed by histology. 5 Local infusion of these higher doses of SNAP and nitroprusside reduced systemic arterial blood pressure (BP), but this was not correlated with the extent of mucosal injury. 6 Furthermore, local infusion of GTN (10-40 mug kg-1 min-1, i.a.) alone. which also reduced BP, failed to induce gastric mucosal damage. 7 These findings suggest that exogenous NO can protect the rat gastric mucosa from damage induced by the vasoconstrictor peptide ET-1, which may reflect local microcirculatory interactions. However, the unregulated release of high levels of NO within the microvasculature induces mucosal injury.