[Effect of nitrates on active transport of iodine]. / Ovplyvnenie aktívneho transportu jódu nitrátmi.

Active iodine transport into the thyrocyte is catalyzed by the transmembrane transport protein Na+/J- symport (NIS) Nitrates can expel iodine from the bond with this transport protein which was found not only in the thyrocyte membrane but also in the cell membrane of the gastric mucosa. The weight of the thyroid gland in mg was significantly greater even when calculated in relation to body weight in the NIT group of rats who were given for 6 days nitrate by gastric tube (100 mg/kg/day) as compared with controls (CON) 17.56 +/- 8.4, 0.07 +/- 0.03/12.10 +/- 9.57, 0.05 +/- 0.03, P < or = 0.01. A lower thyroid activity in per cent calculated per 1 mg of its weight (1.39 +/- 1.0/2.22 +/- 0.9, P < or = 0.01), a higher activity in blood before removal of the thyroid gland (8.54 +/- 4.09/5.45 +/- 2.78) and a lower one after removal of the thyroid gland (1.09 +/- 0.05/0.21 +/- 0.10) before oral administration of I131 in group NIT, suggests a negative effect of nitrates on active iodine transport not only at the level of the thyrocyte but also possible interaction with iodine at the level of the digestive tract. A significantly higher serum level of TT3 in group NIT (0.66 +/- 0.27/0.44 +/- 0.21, P < or = 0.01 regardless of the TSH serum level (2.31 +/- 1.83/2.64 +/- 1.52) and T4 (22.72 +/- 8.2/25 +/- 11.0) suggests a qualitative change in thyroid hormone production in favour of T3 caused even by short-term nitrate administration.

[Nitrate contaminated drinking water from private wells has an impact on the size and functional state of the thyroid gland in schoolchildren]. / Nitrátmi kontaminovaná pitná voda z domácich studní ovplyvnuje vel'kost' a funkcný stav stítnej zl'azy u skolopovinných detí.

UNLABELLED: The authors compared the size of the thyroid gland, assessed by ultrasonographic examination of its volume and the functional state of the thyroid by examination of the serum level of TSH and anti-TPO antibodies in 492 pupils aged 10 and 13 years in two close agricultural areas. The areas differed above all as to the nitrate content of drinking water. In communities where the source of drinking water were private wells (nitrate area), as much as 68.1% of the water samples had a nitrate content > 50 mg/l and 46.4% samples > 100 mg/l. In communities where the source of drinking water was a water main with a known source (control area) the water samples did not exceed 50 mg/l (73.7% > 15 mg/l and 26.3% > 50 mg/l. RESULTS: Pupils from the nitrate area had a larger thyroid gland similarly as older pupils from the control area. A volume above 7 ml/m2 in the nitrate area was recorded in the group of 10-year olds in 25/99 (27.7%) and in the group of 13-year-old ones in 33/154 (21.4%), while in the control area it was in the 10-year-old ones 11/92 (11.9%) and in the 13-year-old ones 16/156 (10.2%, P < or = 0.01). In the nitrate area TSH > 5 mIU/l was recorded in 5.6% and higher anti-TPO antibodies in 2.6% pupils. In the control area the corresponding figure was 1.1% pupils, P < or = 0.01.