In the complex aetio-pathogenesis of gastric ulcer; aggression factors; defence mechanisms and cell-protective factors are involved.

Among the aggression factors; the reactive oxygen species can be found as causal agents but especially as factors that aggravate the primary lesions.

The authors studied the implications of the oxidant /antioxidant system in acute ulcerations of gastric mucosa; induced by non-steroid anti-inflammatory drugs (indomethacin).

An experimental model was realized using Wistar rats that received 50 mg/kg of indomethacin in 5 ml distilled water; through gavage.

The gastric lesions were quantified and their histopathologic examinations were performed.

From the stomach homogenate; the authors determined the parameters of the oxidative stress (lipid peroxides; free malondialdehyde); the antioxidant capacity (hydrogen donor capacity) and nitric oxide.

Significant increases of the oxidative stress parameters and significant decreases of the antioxidant capacity were found.

The nitric oxide did not present significant modifications.

The administration of indomethacin produced gastric ulcerations in which the oxidative stress is implicated.