The effect of iodine on lipid peroxidation and ultrastructure in the thyroids of BB/Wor rats

Effect of dietary canthaxanthin and iodine on the production performance and egg quality of laying hens

In this study, we aimed to evaluate the effect of canthaxanthin (CX) and iodine (I) on the production of laying hens, on counteracting debilitation of the vitelline membrane, and on inhibiting Salmonella growth in eggs stored at 30°C. Three hundred hens were reared in cages. Birds were divided into six feeding groups (10 hens × 5 repetitions) that were administered 0, 3 or 6 ppm of CX and 1 or 10 ppm of I with their diets. Laying rate, egg weights, and feed conversion ratios were controlled. The quality of fresh eggs was assessed in wks 25-26, 48-50 and 62-63 of hens lives. An additional batch of eggs was incubated at the temperature of 30°C, and egg quality changes were monitored on days 3, 6 and 9 of storage. Additionally, eggs collected from four experimental groups of hens whose diets had been iodated with 1 or 10 ppm of I and supplemented with 0 or 6 ppm of CX were infected under laboratory conditions with Salmonella, and incubated for 5 and 10 d. The laying rate, egg weights, and feed conversion ratio were significantly improved. Dietary inclusion of CX contributed to a higher resistance of the vitelline membrane of egg yolks, but only for fresh eggs. Vitelline membrane degradation during egg storage at 30°C was significantly counteracted by dietary inclusion of I at a dose of 10 ppm. The same I dose resulted in the complete inhibition of Salmonella growth until day 10 of incubation, but exclusively for eggs collected from 40-week-old hens. Dietary supplementation with 10 ppm of I was found to impart high level of resistance to the vitelline membrane against the growth of Salmonella in case of eggs stored at 30°C; therefore, I was found to be more beneficial by ensuring longer preservation than that of CX. However, dietary supplementation with CX was found to increase the resistance of vitelline membrane in fresh eggs.

Alterations along the Hypothalamic-Pituitary-Thyroid Axis of the Zebrafish (Danio rerio) after Exposure to Propylthiouracil

In the past, various approaches have been developed to detect adverse effects of pollutants on the thyroid of vertebrates, most of these with special emphasis on the South African clawed frog, Xenopus laevis. Although fish are primarily affected by thyroid-disrupting chemicals, studies into alterations of the thyroid of fish are scarce. Therefore, effects of the reference compound propylthiouracil on histopathology of the thyroid axis were analyzed in a modified early life-stage test with zebrafish (Danio rerio) exposed to propylthiouracil. The test substance induced dose-dependent alterations of thyroidal tissue concomitant with increases in the number of surrounding blood vessels. Despite this massive proliferation of the thyroid, zebrafish were not able to maintain thyroxin concentrations. The pituitary was affected displaying significant alterations in thyroid-stimulating hormone cell counts. Quantitative evaluation of pituitary surface areas revealed a dose-dependent increase of adenohypophyseal tissue. Distinct histopathological effects may contribute to a more easy identification and interpretation of alterations induced by thyroid-disrupting chemicals.

Iodide induced lymphocytic thyroiditis in the BB/W rat: evidence of direct toxic effects of iodide on thyroid subcellular structure

A high dietary iodine intake accelerates the development of lymphocytic thyroiditis (LT) in the BB/W rat. Our previous studies have defined the temporal sequence of the immunological events triggered by excess iodide intake in these animals. It was still not clear, however, whether these observed immunological changes were a direct effect on immune effector cells, or whether they represented a secondary response to a toxic effect of iodine on thyroid tissue. In the present study, the effect of excessive iodine intake on the subcellular structure of the BB/W rat thyroid gland, particularly, whether iodide had a toxic effect independent of its immune response has been examined. BB/W rats were exposed, prenatally through maternal drinking water, to excessive iodide at two doses (Moderate 3 x 10(-6) M iodide/l; High 3 x 10(-3) M iodide/l); a third group of BB/W rats was given tap water; till 12 weeks postnatal age. Two groups of Wistar rats received high dose iodide water or tap water for the same period of time and served as controls. Thyroid gland ultrastructure was determined by electron microscopic (EM) examination. Thyroid 125I uptake and perchlorate discharge tests were also performed in separate experiments. We found that thyroid glands of non-iodine supplemented Wistar rats were morphlogically normal under EM. There were no overt changes in the iodide treated Wistar rats. By contrast, iodide treated BB/W rats exhibited marked accumulation of secondary lysosomes and lipid droplets; markedly swollen and disrupted mitochondria and extreme dilatation of rough endoplasmic reticulum (RER).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute iodine ingestion increases intrathyroidal glutathione

In genetically predisposed individuals, autoimmune lymphocytic thyroiditis (LT) is potentiated by excess dietary iodine (I). There have been data which suggest that oxidative stress may have a role in iodine-induced LT. These in vivo studies were undertaken to examine the effect of iodine on intrathyroidal levels of the potent antioxidant glutathione (GSH) and see if the thyroids of LT-prone BB/Wor rats have aberrant GSH responses after iodine-loading. LT-prone BB/Wor, non LT-prone BB/Wor and Wistar rats were randomized to receive either 0.05% I (as Nal) or tap water. Thyroid and liver homogenates were assayed individually for GSH. Following the administration of 0.05% iodine water overnight, all of the animals demonstrated a rise in intrathyroidal GSH regardless of LT-proneness. To determine whether this was a dose-dependent response, Wis rats were randomized to receive tap, 0.0125%, 0.025%, 0.05%, or 0.075% I, overnight. Intrathyroidal GSH levels rose with increasing iodine concentrations peaking at 0.025% I. Hepatic GSH levels were unaltered by iodine treatment. Ten days of 0.05% I water did not result in any difference between the GSH levels of thyroids from treated and control rats. Frozen sections of the thyroids and livers from iodine-treated rats were compared to tap-water controls after staining with Mercury Orange for GSH and Schiff's reagent for evidence of lipid peroxidation. Iodine-treated thyroids had an apparent shift of GSH staining from the apical border to the cytoplasm. However, there was no Schiff's staining indicative of lipid peroxidation in the iodine-treated thyroids.(ABSTRACT TRUNCATED AT 250 WORDS)