Objectives: 

In the past years, melatonin (M) has been revealed as one of the most promising molecules in the treatment of several inflammatory diseases. For this reason, this study was aimed at assessing the effect of exogenous administration of this indole during the induction process of acute pancreatitis (AP) in rats.

Materials: 

For the induction of experimental AP in Wistar rats, four subcutaneous injections of caerulein (20 mg/kg b.w.) were applied to animals every two hours. M was injected intraperitoneally (25 mg/kg b.w.) 30 min before each caerulein injection. After 8-10 h, rats were sacrificed by decapitation and blood and pancreas samples were collected and processed for serological and histopathological studies, respectively. Lipase, a-amylase, corticosterone, total antioxidant power and cytokines IL-1b;, IL-4 and TNF-a; were determined using commercial kits. ANOVA and Student's t tests were performed for the statistical analysis of the results.

Results: 

Light microscope observations of H&E stained sections revealed the presence of edema, inflammatory cell infiltrate and acinar cell degeneration in the pancreas from animals treated only with caerulein. However, M treatment resulted in a decrease of histological signs of AP, as noted by a similar appearance of M-treated rat samples to those of control pancreas. As expected, during caerulein-induced AP the serum levels of a-amylase and lipase increased significantly. However, M treatment reverted to control values both the levels of these enzymes and also total antioxidant power values, as well as the levels of corticosterone caused by caerulein injections. In addition, M pre-treatment reduced serum levels of proinflammatory cytokines IL-1b; and TNF-a; and increased the levels of the anti-inflammatory cytokine IL-4, induced by caerulein in pancreatitic rats.

Conclusions: 

In conclusion, these findings suggest an anti-inflammatory effect of M in caerulein-induced AP. M may be considered a candidate in the treatment of AP.

Supported by MEC-FEDER grant BFU2010-15049