[Protective effect of melatonin against renal dysfunction following severe burn in rats]

To explore the protective effect of melatonin (MLT) against renal dysfunction in the early stage of burn in rats.

Seventy SD rats were randomly assigned to three groups: sham control (n=10), burn control (n=30) and MLT group (n=30). The 30% total body surface area (TBSA) full-thickness burn was induced by immersing the dorsal skin into boiling water for 30 seconds, while MLT (10 mg/kg, i.p.) was given immediately postburn, and the same dose was repeated once after 12 hours. The contents of malondialdehyde (MDA) and reduced glutathione (GSH) in renal tissue, as well as plasma creatinine (BCr) and urea nitrogen (BUN) levels were measured at 6, 24 and 72 hours postburn, while the activities of glutathione peroxidase (GSH-Px) and myeloperoxidase (MPO) of renal tissue were measured only at 6 hours postburn.

MDA content was significantly increased and GSH content was decreased in renal tissue after a 30 % TBSA full-thickness burn at all time points. Plasma BCr and BUN levels were elevated within 24 hours postburn. All these changes peaked at 6 hours postburn (all P<0.01). Single injection of MLT decreased MDA by 27.8% (P<0.01) but increased GSH by 44.4% (P<0.05). It also inhibited the rise in plasma BCr and BUN levels (P<0.05 and P<0.01). However, repeated MLT injection did not show additional effect on these parameters as single injection of MLT. In addition, single dose of MLT also lowered the MPO level by 30.2% (P<0.05), but did not improve the GSH-Px activity at 6 hours postburn.

Severe burn may result in obvious oxidative stress (within 72 hours postburn) in the kidney with acute renal dysfunction (within 24 hours postburn). Single injection of MLT partially counteracted these changes, due to its high free radical scavenging capacity as well as its inhibitory effect on neutrophil-mediated tissue injury.