Effect of long-term administration of arsenic (III) and bromine with and without selenium and iodine supplementation on the element level in the thyroid of rat

Abstract

The aim of this study was to evaluate the influence of arsenic and bromine exposure with or withour iodine and selenium supplementation on the element level in the thyroid of rats. Four major groups of Wistar female rats were fed with respective diets: group A -standard diet, group B -iodine rich diet (10 mg I/kg food), group C -selenium rich diet (1 mg Se/kg) and group D -iodine and selenium rich diet (as in group B and C). Each group was divided into four subgroups per 7 animals each receiving either NaAsO 2 ip (6.5 mg.kg -1 twice a week for two weeks and 3.25 mg.kg -1 for six weeks) or KBr in drinking water (58.8 mg.l -1 ) for 8 weeks or combined administration of both substances. Remaining subgroup served as controls. After 8 weeks thyroid glands were analyzed by ICP-MS for As, Br, Se, and I content. The exposition of rat to arsenic or bromine causes the accumulation of these elements in the thyroid gland (∼18 ppm of As, ∼90 ppm of Br) and significantly affects iodine and selenium concentration in the thyroid. In iodine and/or selenium supplemented rats the bromine intake into the thyroid was lowered to ∼50% of the level in unsupplemented animals. Also selenium thyroid level elevated due to KBr administration was lowered by iodine supplementation in the diet. The accumulation of arsenic in the thyroid was not influenced by selenium or iodine supplementation; however, As(III) administration increased iodine thyroid level and suppressed selenium thyroid level in selenium or iodine supplemented group of animals.

The Minimal Arsenic Concentration Required to Inhibit the Activity of Thyroid Peroxidase Activity In Vitro

“…Arsenicals, such as sodium arsenite (NaAsO 2 ) and arsenic trioxide (As 2 O 3 ), are also known to disrupt thyroid function. Specifically, these compounds have been shown to alter the function of thyroid hormone nuclear receptors [3], accumulate in thyroid tissue [4], interfere with normal thyroid hormone metabolism [5][6][7], and induce goiter [8,9]. However, to our knowledge, no data is currently available indicating whether or not low levels of these arsenical compounds affect the synthesis of thyroid hormones.…”

Gestational Arsenic Trioxide Exposure Acts as a Developing Neuroendocrine-Disruptor by Downregulating Nrf2/PPARγ and Upregulating Caspase-3/NF-ĸB/Cox2/BAX/iNOS/ROS

“…Also, some histological alterations such as a flattened cell lining epithelium, hyperplasia, edema, atrophy, colloid vacuoles, and destructive degeneration were observed in the fetal thyroid gland at ED 20. Previously, ATO accumulates in the thyroid follicles 70 and binds the protein sulfhydryl group of thyroid peroxidase (THs synthesis) 20,71 decreasing THs levels, 13,72 altering THs-metabolism, 73 perturbing thyroid receptors (TRs), 72,74 and thus initiating goiter. 75 Another possible mechanism is that exposure to arsenic can decrease the levels of selenium (necessary for conversion of T4 to T3) in blood and tissue causing a negative action on thyroid functions.…”

Concentration of Thyrotropic Hormone in Persons Occupationally Exposed to Lead, Cadmium and Arsenic

“…Investigations of Kotyzova et al failed to demonstrate effects of selenium and iodine supplementation on storage of arsenic in rat thyroid glands (in cases of exposure to bromine supplementation with iodine and selenium induced 50% reduction of bromine uptake by thyroid gland). On the other hand, exposure to arsenic induced an increase in iodine concentration and a decrease in selenium concentration in thyroids of animals administered with iodine and selenium [ 46 ]. Meeker et al described a positive relationship between arsenic concentration in blood and serum TSH concentration in 219 men, patients of an infertility clinic.…”