Abstract
Background:
Enteritis is an inflammatory disorder of the intestine characterised by complex immunological responses and subsequent tissue destruction. L-arginine, a semi-essential amino acid involved in nitric oxide generation, demonstrates both protective and pro-inflammatory actions in varying settings. Nonetheless, its involvement in enteritis production and related inflammatory responses is not yet fully understood.

Aim:
This research investigated the long-term impacts of L-arginine administration in rats with enteritis, focussing on proinflammatory cytokines, serum calprotectin, haematological parameters, physiological changes, and histological alterations.

Methods:
Male rats received an oral administration of 500 mg/kg of L-arginine daily for a duration of 30 days to induce enteritis. The control group of rats was administered saline. Body weight, blood tests, and serum levels of TNF-α, IL-6, calprotectin, and C-reactive protein (CRP) were evaluated. The small intestine and spleen were histologically examined to see how much tissue inflammation there was.

Results:
The administration of L-arginine to rats led to a notable decrease in body weight and haematological indices, such as red blood cell count, haemoglobin concentration, and packed cell volume. Levels of inflammatory markers TNF-α, IL-6, CRP, and calprotectin were significantly higher in comparison to control groups. Histological analysis demonstrated vascular congestion and perivascular lymphocytic infiltration in the gastrointestinal tract, as well as lymphoid hyperplasia and blood vessel congestion in the spleen, which indicates active inflammation.

Conclusion:
Extended administration of L-arginine in rats induces enteritis, an inflammatory condition affecting both systemic and localised areas. Proinflammatory cytokines and calprotectin correlate with biochemical and histological markers of inflammation, indicating their utility as biomarkers for the diagnosis and monitoring of enteritis. The findings indicate that L-arginine supplementation should be avoided in contexts associated with intestinal inflammation and underscore potential avenues for therapeutic intervention.

Key words: Calprotectin; Cytokines; Enteritis; Rat Model; L-Arginine.