In Poland, a high level of nitrate and nitrite in food and iodine deficiency have been observed in the last years. The effects of potential goitrogens, namely allylisothiocyanate (SCN-), nitrate (NO3 -) and nitrite (NO2 -) on growth performance, serum hormones (fT4, TSH) and thyroid morphology were investigated in rats. Simultaneously, the potential antigoitrogenic effects of iodine and selenium supplements were studied. In experiment 1, male Wistar rats of an initial body weight of 95 g were fed four experimental diets, based on AIN93G diet for rodents, with 0 or 2 μg iodine (KIO3) supplement per rat per day. The diets were: AIN-93G- control (C), AIN-93G + I (C+I), AIN-93G +SCN- (6 mg/100 g body weight) (SCN), AIN-93G + SCN- (6 mg/100 g body weight) + I (SCN+I), AIN-93G + NaNO3 (300 mg/100 g) (NO3), AIN-93G + NaNO3 (300 mg/100 g) + I (NO3+I), AIN-93G + NaNO2 (25 mg/100 g) (NO2) and AIN-93G + NaNO2 (25 mg/100 g) + I (NO2+I). The diets were fed to eight groups of rats (n=6) for 18 days. Feed intake was restricted to 15 g/day/rat. Body mass of rats was monitored weekly. On day 18, the rats were anaesthetised and their blood was drawn by cardiac puncture. The immulite rat TSH application kit was used to determine TSH concentrations in blood serum. Serum fT4 was determined according to the LIA method. The thyroid glands were excised and processed by the conventional paraffin technique. The growth of rats was not affected by the intake of goitrogens. Serum fT4 concentration tended to decrease by the treatments (C – 24.6, SCN-19.8, NO3 – 21.8 and NO2 – 21.3 pmol/L). At the same time, serum TSH levels were significantly increased after administration of SCN (p<0.02) and NO2 (p<0.05). The histological examination of thyroid glands showed a series of morphological alterations (high follicular epithelial cells and reduced amount of colloid). On the other hand, the rats fed the experimental diets supplemented with iodine (C+I, SCN+I and NO3+I), showed no changes in the parameters studied, compared with the control animals. The only exception were the rats fed NO2+I diet, showing still morphological alterations in their thyroid glands. In experiment 2, male Wistar rats of an initial body weight of 120 g were fed five experimental diets, based on AIN93G rodent diet. The diets were: AIN93G (CON), AIN93G + Se, (Se), AIN-93G + NaNO2 (25 mg/100 g) (NaNO2), AIN-93G + NaNO2 (25 mg/100 g) + Se (NaNO2+Se), AIN-93G + NaNO2 (25 mg/100 g) + Se + I (NaNO2+Se+I). The diets were fed to five groups of rats (n=6) for 18 days. The feed intake was restricted to 15 g/ day/rat. Body mass of rats was monitored weekly. On day 18, the rats were anaesthetised. The thyroid glands were excised and processed by the conventional paraffin technique. The growth of rats was not affected by the dietary treatments. The histological examination of thyroid glands showed a series of morphological alterations in rats fed nitrite diet (NaNO2) and nitrite + selenium diet (NaNO2+Se), whereas in rats fed nitrite + selenium + iodine diet (NaNO2+Se+I), morphology of thyroid gland was similar to that of the control animals (CON). In conclusion, dietary allylisothiocyanate, nitrate and nitrite impair thyroid metabolism in rats and lead to thyroid hypertrophy. At the same time, the goitrogenic effects of allylisothiocyanate and nitrate can be alleviated by dietary iodine whereas the goitrogenic effects of nitrite can be alleviated only by concomitant dietary supplements of selenium and iodine.
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