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Purpose: This study examined the effect of liposomal encapsulation of 99mTc-labeled diethylenetriaminepentaacetic acid (metastable technetium labeled DTPA) on its organ distribution and therapeutic effect of optimized neutral liposomal-DTPA against thorium (232Th)-induced liver toxicity and its accumulation in rat animal model. Materials and methods: 99mTc-DTPA was encapsulated in neutral (dipalmitoylphosphatidylcholine:cholesterol) and positively (dipalmitoylphosphatidylcholine:cholesterol:stearylamine) charged liposomes using thin film hydration method. Comparative efficacy of liposomal and free DTPA (11.2 mg/kg) was examined in terms of its effect on 232Th accumulation and subsequent toxicity in the liver and blood of rat administered with 232Th-nitrate (600 μg/kg). Organ distribution of free or liposomal 99mTc-DTPA was determined by solid scintillation counting and 232Th accumulation by Inductively Coupled Plasma-Atomic Emission Spectroscopy. Results: Neutral liposomes encapsulated with 99mTc-DTPA showed more uptake in liver, spleen and blood than with positively charged liposomal- and free- 99mTc-DTPA. Administration of 232Th-nitrate to rat significantly increased the levels of liver toxicity markers and of oxidative injury, which were found to be restored more significantly by neutral liposomal-DTPA than free-DTPA. The accumulation of 232Th in liver and blood of contaminated mice was found to be decreased more significantly by neutral liposomal-DTPA than by free-DTPA. Conclusions: Decorporation and consequent mitigation of 232Th induced toxicity may be significantly improved by liposomal encapsulation of DTPA, a chelating agent. [ABSTRACT FROM AUTHOR]

Purpose: Thorium (232Th), a heavy metal radionuclide that targets the liver and skeleton, has been shown to accumulate in the central nervous system at low levels. The present study was aimed to investigate neurobehavioural and neurochemical changes in mice treated with 232Th at sub-lethal doses. Materials and methods: Swiss albino mice were administered intraperitoneally with thorium nitrate. The chelation-based therapeutic effect of calcium diethylenetriamine pentaacetate (Ca-DTPA) was tested on the 232Th-treated mice. 232Th localisation was determined in brain regions by the Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) method. Achetylcholine esterase (AChE) activity in different brain regions was evaluated to assess the cholinergic function of mice CNS. Oxidative damage was evaluated by assessing the activities of antioxidant enzymes (i.e., superoxide dismutase and catalase) and the level of lipid peroxidation. The neurobehavioural alteration in the treated mice was studied by the shuttle box method. Results: 232Th accumulation found in different brain regions followed the order: Cerebellum (Cbl) > cortex (Ctx) > hippocampus (Hp) > striatum (Str). However, removal of 232Th by Ca-DTPA was significant from brain regions like Cbl, Ctx and Str but not from Hp. A significant increase in lipid peroxidation and acetylcholine esterase (AChE) activity was observed in the treated mice but activities of superoxide dismutase and catalase was found substantially decreased. 232Th treatment impaired the learning and memory-based neurobehaviour of the mice. Furthermore, our data suggest that Ca-DTPA injection in 232Th-treated animals failed to improve the neurobehaviour of the treated mice, perhaps because Ca-DTPA could not decorporate 232Th or mitigate 232Th-mediated neurochemical changes effectively from/in hippocampus, a brain region implicated in learning and memory response. Conclusion: Administration of 232Th in mice caused neurobehavioural alteration and impairment of cholinergic function, which might be the consequence(s) of oxidative stress induction in different brain regions. [ABSTRACT FROM AUTHOR]

Purpose: Thorium (232Th, IV) preferentially accumulates in the liver, femur and spleen, which necessitates evaluation of its toxic effect in these organs. The present study was aimed at evaluation of liver function, oxidative stress and histological alterations in these organs. Materials and methods: Swiss albino mice were administered either with Thorium nitrate (10 mg/kg body weight/day equivalent to 1090 pCi/kg body weight/day) for 30 days (1/40th dose of LD50/30; the dose of thorium required to kill 50% of the test cohort within 30 days) intraperitoneally or with calcium salt of diethylenetriamine pentaacetate (Ca-DTPA, 100 μmole/kg body/weight) intravenously or both. Liver function tests and oxidative damage was assessed. The concentration of Th in the tissues was determined by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) method. Results: Administration of Th prevented the increase in the body and liver weight and altered liver functions. Th treatment to mice showed a decrease in the activities and gene expression of antioxidant enzymes, and increased lipid peroxidation and protein carbonylation. The extent of observed oxidative damage was correlated with accumulation of Th in examined organs and further associated with histological alterations. Furthermore it was found that these effects were significantly lower when the chelating agent, Ca-DTPA, was given 1 h after Th injection. Conclusion: Administration of subtoxic concentration of Th to mice markedly altered the liver functions and induced oxidative stress in the liver, femur and spleen of mice. The results further demonstrated that Ca-DTPA significantly protected mice against the toxic effects of Th. [ABSTRACT FROM AUTHOR]