The protective role of melatonin on L-arginine-induced acute pancreatitis in adult male albino rats.

BACKGROUND: Acute pancreatitis (AP) is an inflammatory disease that has an increasing incidence worldwide. It is associated with high morbidity and mortality rates ranging from 15-40% in its severe form. Oxidative stress plays an important role in pancreatic acinar cell injury in case of AP. Melatonin is proven to have both antioxidant and anti-inflammatory effects. The aim of the work was to investigate the protective role of melatonin (Mel) against L-arginine (L-arg)-induced AP in adult male albino rats.

MATERIALS AND METHODS: Thirty six adult male albino rats were used in this study. Animals were divided into 4 groups; Control group (Group A; N=6), Mel group (Group B; N=6), L-arg group (Group C; N=12) receiving two doses of L-arg injection with 1 hour interval in-between, and L-arg+Mel group (Group D; N=12) receiving Mel 1 hour after each L-arg injection. Twenty four hours after the second L-arg injection, the serum levels of amylase (AM), lipase (LP), interleukin-6 (IL-6) and tumor necrotic factor-α (TNF-α) were determined. Then, pancreatic specimens were processed for histological and immunohistochemical staining with vascular endothelial growth factor (VEGF) and the area percentage of VEGF and collagen content were measured by digital image analysis.

RESULTS: Microscopic examination revealed that animals received L-arg only (Group C) showed loss of the pancreatic lobular architecture with marked fibrosis, acinar degeneration, inflammatory reaction and marked edema with vascular congestion. Also, L-arg-induced AP caused a significant elevation of the serum levels of AM, LP, IL-6. All these histo-pathological and serological parameters were markedly improved by Mel administration.

CONCLUSIONS: Mel exhibits strong therapeutic effects in the course of AP. Hence, the use of Mel as adjuvant treatment in AP is recommended.