Melatonin reduces inflammation and recovers endogenous ghrelin in acute necrotizing pancreatitis in rats

The present study aimed to evaluate, the therapeutic effects of melatonin on either ghrelin secretion or gastric mucosal injury in acute necrotizing pancreatitis (ANP). ANP was induced in rats by L-arginine. Prior to L-arginine injection, the rats were pre-treated with melatonin for 30 min. Following the last injection, the animals were sacrificed at different time-points. The levels of ghrelin and melatonin in the serum and gastric tissue were detected by ELISA. Levels of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6 and malondialdehyde (MDA) as well as total superoxide dismutase (T-SOD) activities in gastric tissue were measured. In rats with ANP, acute gastric injury was observed, and the levels of MDA, SOD, TNF-alpha and IL-6 were significantly increased. The melatonin levels in serum or gastric tissue peaked at 6 h and returned to normal levels at 12 h after melatonin was administered. However, ghrelin remained at low levels during the first 12 h, but it recovered at 24 h and continued increasing, while the levels of oxidative stress damage and activity of inflammatory factors were decreased. The protective effects of melatonin on acute gastric injury during the early stages of ANP may be mediated through anti-oxidative and anti-inflammatory activities, while at advanced stages of ANP, it may be mediated through the recovered endogenous ghrelin.