Effects of Mercuric Chloride and Potassium Dichromate on the Thymic Ultrastructure

염화제이수은 및 중크롬산칼륨이 가슴샘의 미세구조에 미치는 영향

Ultrastructure of mouse thymus was evaluated, following the administration of potassium dichromate and mercuric chloride, the heavy metals of evironmental pollutants. Potassium dichromate (20 mg/kg) or mercuric chloride solutions (10 mg/kg) were subcutanously injected to the mice. Six hours, three days and two weeks after the injections, animals were sacrificed. Thymic tissues were fixed in 2.5% glutaraldehyde-1.5% paraformaldehyde solutions. The procedure was followed by the fixation in 1% osmium tetroxide solutions. Washed and dehydrated tissue-blocks were embedded in the araldite mixture. Ultra-thin sections were stained with uranyl acetate-lead citrate solutions. Results observed were as follows: 1. In electron microscopy, cortical population of thymocytes in the thymus of experimental groups were reduced. especially in the outer cortex. Subcapsular cortices of potassium dichromate treated mice were filled with many epithelial reticular cells, whereas the similar area of mercuric chloride-treated mice exhibited large intercellular spaces. 2. In the thymus of mercuric chloride treated group, large intercellular spaces were formed by shrinkage of epithelial reticular cells, and the space was invaded by numerous cytoplasmic projections of macrophages. Thymocytes nuded out from the shrunken cytoplasm of epithelial reticular cells, presented numerous microvilli. 3. In the thymus of potassium dicromate treated group, many activated macrophages and plasma cells migrated into thymic cortices. 4. In the perivascular spaces of thymic cortices of potassium dichromate- and mercuric chloride-treated mice, activated macrophages. plasma cells, collagen fibrils, and flocculent substance of exudated materials were exhibited. From the above findifgs, it was concluded that potassium dichromate or mercuric chloride could disturb the normal differentiation or 'education' of T cells in the thymic cortex. In turn, these heavy metals may hurt the immunological defense mechanism.