Delayed Effect of Thorotrast Deposition in Humans: Carcinogenesis and Suppression of the Reticuloendothelial System

Abstract

Thorotrast is a colloidal solution containing 20% thorium (232Th), and used to be used primarily in diagnostic radiology for visualization. Once thorotrast is infused into the body, it is not eliminated easily. Over 90% of thorotrast forms deposits. It emits a-rays, and thorotrast-injected patients are semipermanently irradiated from a-particles deposited in the body. Thorotrast gives rise to malignant tumors by delayed effect of deposition, and especially liver cancer is highly associated with thorotrastosis. Deposition of thorotrast as an exogenous substance inhibits phagocytosis by suppressing the reticuloendothelial system (RES) as well and bringing about a Shwartzman preparatory state (preshock state) in patients. A majority of thorotrast-injected patients died abruptly. This short natural history of thorotrastosis is thought to have some relation to RES suppression by long-term thorotrast deposition resulting in vulnerability to shock and infection.

Biodistribution and Ultrastructural Localization of Single-Walled Carbon Nanohorns Determined In Vivo with Embedded Gd2O3 Labels

“…Alternatively, those taken up by macrophages in the airways may have been excreted via respiration. 33 The slight increase in the stomach/intestine might indicate that Gd 2 O 3 @SWNHag was excreted via a respiratory pathway, captured in sputum, and swallowed to reach the stomach and intestine. An alternate explanation could be that some of the Gd 2 O 3 @SWNHag in the liver was exported to the stomach/intestine through the gallbladder.…”

“…The decrease of Gd 2 O 3 @SWNHag in the lungs suggested that the aggregates may have been exported from the lungs to other organs. Alternatively, those taken up by macrophages in the airways may have been excreted via respiration …”

“…The high electron scattering ability of Gd provided high contrast for clear detection by TEM and, because Gd is not found naturally in the body, it could be clearly identified with energy dispersive X-ray spectroscopy (EDX). The TEM coupled with elemental analysis by EDX or electron energy loss spectroscopy (EELS) is a conventional technique for localizing fine particles in various materials, including living tissues. − …”