Sodium valproate effect on the structure of rat glandule thymus: Gender-related differences

Sodium valproate (VPA) was shown to inhibit cell growth mechanisms such as cell cycle arrest, proliferation suppression, increase of apoptosis. Many aspects of the contribution of the VPA pharmacological mechanisms and their significance in gender-related processes have not been investigated. In our study, we have tested hypothesis that the influence of VPA on thymus weight and structure might be gender-related. The thymus of Wistar rats of both genders aged 8 weeks was investigated in the following groups (n = 6 each): controls, treated with VPA, castrated male and female treated with VPA, and the castrated control of both genders. The thymus weight, structural changes and area of cortical and medullar parts of the gland in slides stained with hematoxylin and eosin and immunohistochemically were assessed. A comparison of thymus weight of castrated male and of castrated VPA-treated male rats showed a significant thymus weight loss after VPA treatment (0.66 ± 0.04 g vs. 0.43 ± 0.03 g, p < 0.05). The treatment with VPA caused an about 6-fold (0.39 ± 0.12 vs. 0.07 ± 0.03) increase of Hassall's corpuscles (HCs) numbers per 1 mm2 in male and more than 4-fold increase (0.46 ± 0.07 vs. 0.10 ± 0.04) in female rats. In castrated males and females, the HCs number was also increased, but this increase was statistically significant only in male animals vs. controls (0.46 ± 0.10 vs. 0.07 ± 0.03, p < 0.001 in males; 0.29 ± 0.13 vs. 0.10 ± 0.04, p > 0.05 in females). When castrated male and female rats were treated with VPA, further increase of HC numbers was found. In our study, VPA has inhibited the proliferative capacity of thymocytes by diminishing the thymus weight and inducing a differentiation of thymic medullar epithelial cells into HCs. The diminishing of the gl. thymus weight under the influence of VPA was significant in castrated male rats. The number of HCs increased in animals of both genders under the influence of VPA. Gender differences in HCs development were noted in castrated animals.