The Electron Microscopy of the Response of Follicular Epithelium Cells of Rat Thyroid to Autolysis, Ligation, and Irradiation by Iodine-131

Abstract

Electron and light microscopy were used to study intracellular changes in follicular epithelium cells of rat thyroid after (1) autolysis, in which a lobe was left in a dead animal for a specified time, (2) ligation, in which the inferior thyroid artery supplying the left lobe was tied off and the isthmus severed, and (3) irradiation with intraperitoneally injected radioiodine. Visible responses of follicular cells to autolysis, ligation, and treatment with I131 were essentially the same and consisted in alteration of endoplasmic reticulum to spherical vesicles; swelling of mitochondria and their apparent subsequent degradation to lipidlike granules; and the presence of membranelike structures in cell cytoplasm and the follicular lumen. Endoplasmic reticulum of I131 treated cells responded before other cytoplasmic components showed any change, however. Autolyzed nuclei were optically lighter after staining than normal nuclei and less electron-dense than nuclei of follicular cells of normal, irradiated, and ligated thyroids. Estimated dosage, time, and effect relationships are given for I131 experiments. Treatment with radioiodine resulted in rounding of endoplasmic reticulum in some cells at 24 hours. Two days after such treatment profound intracellular changes were evident. It is suggested that rounding of endoplasmic reticulum and swelling of mitochondria might be attributed to osmotic and surface tension changes within the cytoplasmic environments of these organelles. Mechanisms for the reduction of the endoplasmic reticulum to small spherical vesicles are postulated. It is also suggested that bizarre membranelike structures appearing in severely injured cells and in the colloid lumen might be the result of fixation and sectioning through unusual liquid interfaces, these interfaces are considered to arise from changes in colloidal systems after destruction of organelles and the presence of debris.