Antithyroid and goitrogenic effects of coal-water extracts from iodine-sufficient goiter areas

Goiter in iodine-sufficient areas has been linked to water-borne goitrogens in watersheds and aquifers rich in coal and shale. In the present study, the potential antithyroid and goitrogenic effects of coal-water extracts (CWE) were investigated in vivo in rats after chronic and acute oral administration of CWE, and in vitro by a thyroid peroxidase (TPO) enzyme system. CWE was prepared by continuous extraction of ground (40 mesh) Appalachian coal with goitrogen-free water (GFW). Female Buffalo rats fed on Purina iodine-rich diet (12 micrograms I-/day/rat), were given ad lib CWE (50 mg/ml; approximately 20 mL/day/rat) or GFW (controls) for 2 months. At the end of the experiment, 125I 1 microCi, was injected i.p. and 4 h later the thyroid glands were removed, weighed, and analyzed histologically and for total 125I and 125I-labeled compounds. Rats on CWE had larger thyroid glands [7.2 +/- 0.3 mg/100 g (mean +/- SE) vs 5.0 +/- 0.5 controls; p < 0.005] with distinct histological changes of smaller thyroid follicles, some with columnar epithelium, and with more dense colloid than in controls, and had significant inhibition of the coupling mechanism for production of thyroid hormones [125MIT + DIT/125T3 + T4: 5.1 +/- 0.2 vs 3.9 +/- 0.1 controls, p < 0.005; and 125T3 + T4 (%): 10.6 +/- 0.3 vs 12.6 +/- 0.4 controls, p < 0.005]. Female Sprague-Dawley rats under the same conditions as Buffalo rats were given acutely by GI tube 2 mL of CWE (5 g/mL) or GFW (controls).(ABSTRACT TRUNCATED AT 250 WORDS)