The retention and elimination of colloidal thorium dioxide in the albino rat following protracted administration

Long term effects of thorium dioxide (thorotrast) administration on human liver. Ultrastructural localization of thorium dioxide in human liver by analytical electron microscopy

The ultrastructual localization of thorium dioxide was examined in liver biopsy specimens from two patients injected more than 30 years before with thorotrast. An energy dispersive X-ray microanalysis spectrometer (Kevex 5100) was used to identify thorium in the liver tissue. By electron microscopy, most of the thorium particles were found in the cells of the reticuloendothelial system, such as macrophages of the portal triad and Kupffer cells in the hepatic sinusoid. Thorium dioxide particles were mainly located within the phagosomes, but larger aggregates existed in the cytoplasma with no visible limiting membrane. In addition, the deposition of thorium granules in a few hepatocytes was also confirmed by electron microscopy. This fact indicates that two main pathways of elimination are still functioning in the late period, but the hepatocytic pathway appears to be less effective than the reticuloendothelial system.

Investigations into human thorotrastosis. Tissue concentrations of 232-Th and late effects in 13 autopsy cases

The subjects of investigation were 13 dead thorotrast patients, 10 male, 3 female, with ages ranging from 45 to 79 years. Two thousand organ and tissue specimens were investigated by means of autopsy and by both microscopic-autoradiographic and neutron activation analysis in order to detect late effects and to determine on approximate mean concentration of 232Th (mg per g of tissue). A comparison between late effects and concentrations of the dye medium led to the following conclusions: 1. 232Th is, after intravascular injection, deposited in all organs and tissues of the human body. 2. The highest mean concentrations are shown in the spleen, liver, bone marrow, and lymph nodes. 3. The distribution of 232Th is inhomogeneous in all organs and tissues. The variations of maximum and minimum concentration lie around factor 2.2 X 10(0)-2.4 X 10(5). 4. Late effects occur only in spleen, liver, lymph nodes, and bone marrow, but not in organs and tissues that show a mean concentration of 232Th under 10(-1) mg per g tissue. 5. It is highly probable that tumors of thorotrast patients in organs other than spleen, liver lymph nodes, and bone marrow are not caused by deposition of 232Th or ThO2.