Pathologic features of iodide toxicosis in calves.

Forty Holstein-Friesian heifer calves were divided into four groups of ten each and dosed orally with ethylenediamine dihydriodide to provide 0, 50, 250, or 1,250 mg of iodide/animal each day. Five calves in each group were given thyrotropin-releasing hormone at 4-week intervals. Two calves given 1,250 mg of iodide (active ingredient)/day died by 70 days and had severe bronchopneumonia. At 6 months, the remaining 38 calves were killed. Pneumonia was evident in calves given iodide, with the severity apparently dose-related. Squamous metaplasia of tracheal epithelium occurred in all calves given 1,250 mg of iodide. Similar changes were seen in the interlobular duct of the parotid gland of two calves given 1,250 mg of iodide and in one calf given 250 mg. Scanning electron microscopy revealed changes in the tracheal mucosa, the severity of which were related to the dose of iodide fed. Changes in the thyroid glands of calves given 1,250 mg of iodide included large follicles, flat epithelium, and large amounts of colloid. In calves given 1,250 mg of iodide plus thyrotropin-releasing hormone, the histologic features of the thyroid glands were similar to controls. Serum vitamin A concentrations were less in calves given 1,250 mg of iodide relative to that of control calves. In general, calves were able to compensate fpr excessive dietary iodide after an initial period of an apparent increased susceptibility to respiratory tract infection.

Polybrominated biphenyl toxicosis in rats fed an iodine-deficient, iodine-adequate, or iodine-excess diet.

Young male Sprague-Dawley rats were fed 0, 1, 10, or 100 ppm of polybrominated biphenyls (PBB) in iodine-deficient, iodine-adequate (0.2 ppm), or iodine-excess (1000 ppm) diets. Six rats in each of the 12 groups were killed at 30 days and the remaining six in each group at 60 days. Growth rates were similar in all rats fed diets containing 0, 1, or 10 ppm PBB but were slower from 30 to 60 days in rats given 100 ppm PBB. Results of routine hematologic examinations and urinalyses were essentially normal. Although liver weights were substantially increased by PBB, the smallest increases were in rats fed an iodine-deficient diet. Thyroid weights were increased by iodine deficiency and by 10 and 100 ppm PBB. Electropherograms of serum proteins, serum lipoproteins, and LDH isozymes at 60 days from rats given PBB indicated hepatic alterations, but changes were least dramatic in rats fed an iodine-deficient diet plus PBB and most severe in rats fed iodine-excess diets plus PBB. Hepatic lesions were basically similar to those previously described except that bile duct proliferation was seen at 60 days only in rats fed an iodine-deficient diet and 100 ppm PBB. Histologic changes in thyroid glands were associated with iodine deficiency and with PBB. The iodine-excess diet plus 100 ppm PBB induced squamous metaplasia of respiratory bronchiolar epithelium. These results indicate interrelationships between PBB and iodine which may affect the toxicosis caused by PBB.