Histological, ultrastructural and immunohistochemical study of the effect of estrogen intake on the thymus of female albino rat before and after puberty

ABSTRACT

This study was conducted on 24 healthy female albino rats to domenstrate histological and immunohistochemical changes which may occur in the thymus after injection of diethylstilbestrol. The animals were divided into two main groups [12 animals each] prepubertal and postpubertal. Each group were subdivided into control and treated groups [6 animals each]. The control groups were subcutaneously daily injected with corn oil. While, the treated groups were injected with 17.5 microg/ 100 grams body weight of diethylstilbesterol. After 14 days of injections. the thymuses were dissected, divided into two parts, one for histological and estrogen receptors study, while the second part for ultrastructural study. The thymus of the control prepubertal group appeared with many packed thymocytes and dark star shaped reticular epithelial cells in-between. However, control postpubertal thymus appeared with mild thickening of interlobular septa, less packed thymocytes. Many cells noticed with small electron dense nuclei, peripheral condensation of heterochromatin, irregular nuclear membrane and unrecognized cell organoids [apoptotic cells]. In addition to pale cells with large wide processes and dark star shaped cells with slender narrow processes in-between thymocytes. Sections of treated prepubertal thymus glands showed, thickening of the thymic capsule with fat infiltration and loss of distinction between the cortex and medulla. There was an increase in the number of Hassall s corpuscles and large reticular cells with large pale nuclei and pale cytoplasm in the thymic medulla. Additionally, transmission electron microscope study of this group revealed, many cells at different stages of apoptotsis. However, treated postpubertal thymus appeared with marked depletion of the cortical thymocytes of some Lobules and many cells at different stages of apoptosis. The immuriostainirig for estrogen receptor showed that, estrogen receptor was expressed in some thymic cells of the cortex especially, the subcapsular, around interlobular septa and at the corticomedullary zones. However, the thymocytes appeared negatively reacted. In the medulla, the Hassall s corpuscles were weak positively reacted. The intensity of the reaction appeared varied according to the age of the animals and appeared to increase after the treatment. In conclusion, estrogen administration revealed many histological and immunohistochemical changes in pre and postpubertal thymuses which may alter the immune responses. So, contraception methods must be chosen carefully especially in young aged females