Estradiol induced thymus alterations in adult male albina rat: histological and immunohistochemical study

ABSTRACT

Thymus is responsible for generation of most of circulating T-cells, Although estrogen regulates thymic development, exposure to increasing amounts of exogenous estrogen would modulate thymus structure, function as well as immune system. Was to study the structural changes of thymus after estradiol injection in an attempt to verify the mode of action. 40 adult male albino rats were used dividing into control and experimental groups. Each animal of experimental groups [B 1, B2 and B3] was injected subcutaneously with 5, 25 and 50 mg/kg body weight of estradiol valerate [E2], respectively daily for two weeks. Thymus was dissected and weighted. One lobe was processed for paraffin sections and stained with TUNNEL method to demonstrate apoptosis and the other one used to be examined by transmission electron microscope. Thymus was shrunk and its weight was significantly decreased only in subgroups B2 and B3. Their LM examinations showed degenerated thymocytes and epithelial cells with dense bodies and debris in between intact cells. Large cells enclosed disrupted cells within their cytoplasm. EM examination revealed degenerated thymocytes exhibiting criteria of apoptosis, apoptotic bodies, degenerated epithelial cells and vacuoles of different sizes and shapes inside or outside the cells. Large cells exhibited criteria of epithelial cells enclosed within their cytoplasm intact cells, apoptotic cells, apoptotic bodies and lysosomes were observed. Macrophages with lysosomes and tissue debris were also recorded. Immunohistochemical studies revealed marked increase in the dense brown apoptotic nuclei in subgroups B2 and B3 comparing with control. Estradiol induced involution and degeneration of thymus through increasing apoptosis of thymocytes