Studies on the Antithyroid Activity of Naturally Occurring L-5-Vinyl-2-Thiooxazolidone and Its Urinary Metabolite in Rats

Abstract

Rats were force fed a single dose of 20, 40, 80, 160, 320, 640, 1280 and 2560 μg L-5-vinyl-2-thiooxazolidone (VTO) and injected with 131I one hour later. The 131I uptake, biosynthesis of thyroid hormones and PB131I were measured 4 h after the administration of 131I. Under these conditions, a higher antithyroidal effect with VTO was found in rats fed a normal diet (ND) for 10 days before the experiment as compared with rats fed a low iodinediet (LID) for the same period. The results are described in detail. Similar doses of VTO were force fed to groups of rats fed LID daily for 20 days. The animals received 1 μCi 125I per 15 ml of drinking water for 30 days before sacrifice. One hour after the last dose of VTO they were injected with μCi 131I and killed 4 h later. In addition to the parameters presented above the thyroid weight, total 125I in the thyroid and PB125I were measured. The inhibition of thyroid activity was in direct relation to the dose of VTO administered. Finally, ethereal extracts of urine of rats kept in metabolic cages and force fed a single dose of 10 mg VTO were prepared and the dried extract was dissolved in methanol and applied to the chromatographic paper. In two chromatographic systems (1. water saturated chloroform, 2. n-butanol:acetic acid:water) two compounds were detected, one of which (Compound A) was chromatographically identical with VTO and the other (Compound B) was unknown. The Compound B was extracted from chromatograms, its UV-absorption spectrum was measured and its antithyroid activity was tested in rats. The 131I uptake was significantly inhibited following a single administration of 640 μg Compound B.

Concentrations of thiocyanate and goitrin in human plasma, their precursor concentrations in brassica vegetables, and associated potential risk for hypothyroidism

“…From the previous data of Langer et al, 23 who reported that 77 lmol of goitrin did not decrease thyroidal radioiodine uptake, 23 it is reasonable to infer that a single serving of brassica vegetables with less than 70 lmol of progoitrin would be unlikely to result in decreased thyroid hormone production in humans. Specifically, ingestion of commercial broccoli and broccoli rabe, which each contain less than 10 lmol progoitrin per 100-g serving, would appear to pose minimal risk of thyroidal toxicity.…”

“…One study assessed the change in radioactive iodine uptake by the thyroid glands of human subjects following the administration of recrystallized goitrin. 23 The authors reported that 25 mg (194 lmol) was the minimal amount of goitrin required to decrease the uptake of radioiodine; in contrast, a smaller ingested amount, 10 mg (70 lmol), caused no inhibition of uptake.…”

“…The brassica with the highest total indole glucosinolate concentration was B. oleracae kale (840 lmol/100 g), which did not contain any progoitrin, but the B. napus kale (465 lmol/100 g) had a progoitrin concentration of 176 lmol/100 g, putting it into the category of potential risk for thyroid damage. 23 Progoitrin concentrations in brassica vegetables that produce goitrin upon mastication Based on the measurements by Langer et al, 23 who investigated goitrin doses that impaired thyroidal iodine uptake (i.e., 70 lmol was associated with no inhibition, whereas 194 lmol inhibited iodine uptake), the brassica vegetables were categorized into 3 classes: (1) those with progoitrin concentrations over 100 lmol/100 g of fresh weight [i.e., the Siberian (Russian) kales belonging to the species B. napus, one collard (B. oleracae), and one Brussels sprout (B. oleracae)]; (2) those with goitrin concentrations between 10 and 100 lmol/100 g of fresh weight [i.e., Chinese cabbages (B. rapa), some collards, and Brussels sprouts]; and (3) those with goitrin concentrations less than 10 lmol/100 g of fresh weight [i.e., turnip tops, some Chinese and Japanese greens, commercial broccoli rabe (B. rapa), commercial …”

Glucosinolates and Glucosinolate Derivatives: Implications for Protection Against Chemical Carcinogenesis

“…The intensity of these effects varies with the animal species and, of course, the amount of GSL in their food (Bourdon et al 1981 ;Butler et al 1982;Bell, 1984;Etienne & Dourmad, 1987). In humans, reduced iodine uptake by the thyroid gland was reported after daily ingestion of 500 g cabbage for 2 weeks (Langer et al 1971) or after a single meal of 300 to 500 g swede or turnip (Greer & Astwood, 1948). However, a more recent study by McMillan et al (1986) did not lead to hypothyroidism in human volunteers consuming 150 g Brussels sprouts daily for 4 weeks.…”

“…Goitrin (5-vinyloxazolidine-2-thione), one of the major derivatives of progoitrin, has been the most extensively studied GSL derivative, as far as toxicity is concerned. This goitrogen, very potent even at low doses (Krusius & Peltola, 1966;Langer & Michajlovskij, 1969;Akiba & Matsumoto, 1976), can induce decreased uptake of iodine by the thyroid gland in humans (Astwood et al 1949) and in rats, modify the triiodothyronine : thyroxine ratio and alter the histological pattern of the thyroid in rats (Lo &Hill, 1971 ;Bell et al 1972;Lo & Bell, 1972). It seems that goitrin interferes with organic iodination of thyroxine precursors in the gland, thus leading to compensatory goitre (Akiba & Matsumoto, 1976;Elfving, 1980).…”