Age-related effects of melatonin administration on spleen histology in rats

In this study, the effects of melatonin on spleen tissues of young and old rats were investigated. Sections of spleen tissues were stained with Hematoxylin-Eosin (H&E), Periodic acid-Schiff (PAS) and silvering (reticulin) stains and analyzed under light microscope. Age-related histologic changes in spleen tissue were evaluated. It was observed that the tissue integrity of the spleen structure was preserved in young rats. In old rats, some degenerations were detected in the structural elements forming the parenchyma and stroma of the spleen tissue. Atrophied lymph follicles were observed in the white pulp of old rats. In the red pulp, increased hemosiderin pigment and hollow round clusters of damaged erythrocytes in the lumen of some venous sinuses were observed. Reduced lymphocyte cell population was observed in both white and red pulp. The marginal zone separating the red pulp and white pulp of the spleen could not be completely observed in old rats. The dense reticular fibril network forming the splenic stroma was not well organized. In melatonin-treated old rat groups, it was determined that the white pulp ratio increased and the density of hemosiderin pigments decreased in the red pulp. It was also observed that melatonin increased the cell population in both white and red pulp. It was observed that the integrity of the reticular fiber network forming the splenic stroma was preserved and fiber support around the sinuses was provided. According to the results of histological and histomorphometric analyses, it can be stated that melatonin application partially improves the tissue damage caused by the aging process in the spleen tissue.