Repeated KI Prophylaxis in Case of Prolonged Exposure to Iodine Radioisotopes: Pharmacokinetic Studies in Adult Rats

Treatment of radiological contamination: a review

After nuclear accidents, people can be contaminated internally via ingestion, inhalation and via intact skin or wounds. The assessment of absorbed, committed doses after internal exposure is based on activity measurement byin vivoorin vitrobioassay. Estimation of dose following internal contamination is dependent on understanding the nature and form of the radionuclide. Direct counting methods that directly measureγ-rays coming from within the body or bioassay methods that measure the amount of radioactive materials in urine or feces are used to estimate the intake, which is required for calculating internal exposure doses. The interpretation of these data in terms of intake and the lifetime committed dose requires knowledge or making assumptions about a number of parameters (time, type of exposure, route of the exposure, physical, biological and chemical characteristics) and their biokinetics inside the body. Radioactive materials incorporated into the body emit radiation within the body. Accumulation in some specific organs may occur depending on the types of radioactive materials. Decorporation therapy is that acceleration of the natural rate of elimination of the contaminant will reduce the amount of radioactivity retained in the body. This article presents an overview of treatment of radiological contamination after internal contamination.

Effects of repetitive Iodine thyroid blocking on the foetal brain and thyroid in rats: a systems biology approach

A single administration of an iodine thyroid blocking agent is usually sufficient to protect thyroid from radioactive iodine and prevent thyroid cancer. Repeated administration of stable iodine (rKI) may be necessary during prolonged or repeated exposure to radioactive iodine. We previously showed that rKI for eight days offers protection without toxic effects in adult rats. However, the effect of rKI administration in the developing foetus is unknown, especially on brain development, although a correlation between impaired maternal thyroid status and a decrease in intelligence quotient of the progeny has been observed. This study revealed distinct gene expression profiles between the progeny of rats receiving either rKI or saline during pregnancy. To understand the implication of these differentially expressed (DE) genes, a systems biology approach was used to construct networks for each organ using three different techniques: Bayesian statistics, sPLS-DA and manual construction of a Process Descriptive (PD) network. The PD network showed DE genes from both organs participating in the same cellular processes that affect mitophagy and neuronal outgrowth. This work may help to evaluate the doctrine for using rKI in case of repetitive or prolonged exposure to radioactive particles upon nuclear accidents.

Proteomic Analysis of Iodinated Contrast Agent-Induced Perturbation of Thyroid Iodide Uptake

(1) Background: We recently showed that iodinated contrast media (ICM) reduced thyroid uptake of iodide independently of free iodide through a mechanism different from that of NaI and involving a dramatic and long-lasting decrease in Na/I symporter expression. The present study aimed at comparing the response of the thyroid to ICM and NaI using a quantitative proteomic approach. (2) Methods: Scintiscans were performed on ICM-treated patients. Micro Single-Photon Emission Computed Tomography (microSPECT/CT) imaging was used to assess thyroid uptakes in ICM- or NaI-treated mice and their response to recombinant human thyroid-stimulating hormone. Total thyroid iodide content and proteome was determined in control, NaI-, or ICM-treated animals. (3) Results: The inhibitory effect of ICM in patients was selectively observed on thyroids but not on salivary glands for up to two months after a systemic administration. An elevated level of iodide was observed in thyroids from NaI-treated mice but not in those from ICM animals. Exposure of the thyroid to NaI modulates 15 cellular pathways, most of which are also affected by ICM treatment (including the elF4 and P706SK cell signaling pathway and INSR identified as an upstream activator in both treatments). In addition, ICM modulates 16 distinct pathways and failed to affect thyroid iodide content. Finally, administration of ICM reduces thyroid-stimulating hormone (TSH) receptor expression which results in a loss of TSH-induced iodide uptake by the thyroid. (4) Conclusions: Common intracellular mechanisms are involved in the ICM- and NaI-induced reduction of iodide uptake. However, ICM fails to affect thyroid iodide content which suggests that the modulation of these common pathways is triggered by separate effectors. ICM also modulates numerous distinct pathways which may account for its long-lasting effect on thyroid uptake. These observations may have implications in the management of patients affected by differentiated thyroid carcinomas who have been exposed to ICM. They also provide the basis for the utilization of ICM-based compounds in radioprotection of the thyroid.