Abstract

In recent studies, it has been reported that the widely used immunosuppressive agent, cyclosporine A (CyA), causes tissue damage and that free oxygen radicals play a role in this damage. Melatonin, which is the most important indoleamine released by the pineal gland, is a free radical scavenger and an antioxidant agent. In this study, we aimed to study histopathologically the probable positive effects of Melatonin on CyA induced lung tissue damage. Four groups, each with 8 rats, were used in this study: Group 1; control, Group 2; 4 mg/kg/day intraperitoneal (i.p.) melatonin, Group 3; 10 mg/kg/day subcutaneous (s.c.) CyA and Group 4; 4 mg/kg/day melatonin (i.p.) plus 10 mg/kg/day CyA (s.c.). The study lasted for 28 days for each group. At the end of this period, the rats were killed with lethal anesthesia. Their lungs were removed and embedded in paraffin blocks before being processed for microtome. The preparations were stained with Haematoxylene-Eosin (H-E), and Masson’s trichrome dyes. Both control and Melatonin groups appeared normal. In the CyA group, congestion of the parenchyma, perialveolar edema, perivascular and peribronchial infiltration and thickening of interalveolar septum as a result of an increase in connective tissue were observed in the rat lungs. In the CyA plus melatonin group, histopathological findings were significantly milder than those of the CyA group. Furthermore, mild congestion and edema was encountered only in rare areas. It was concluded that CyA dependent damage may be reversible and that this damage may be significantly decreased by melatonin administration.