Effects of High Doses of Sodium Metavanadate on the Thyroid Status in Rats

Abstract

Introduction: The widespread use of vanadium in the metallurgical industry leads to its high content in the workplace air, which poses a threat to human health both in the workforce and the community. Vanadium accumulates in many organs and has a toxic effect; yet, studies of its effects on the thyroid gland are scarce and narrowly focused. This study is aimed at establishing the effect of vanadium on the functioning of the thyroid gland. Objective: To establish thyroid status in rats after a single intraperitoneal injection of sodium metavanadate. Materials and methods: Twenty-six male Wistar rats aged 3 months weighing more than 200 g were divided into a control group (10 animals) exposed to distilled water and two exposure groups (V11 and V18) of eight animals each intraperitoneally exposed to 11 and 18 mg of sodium metavanadate per kg of body weight, respectively. Serum levels of the thyroid-stimulating hormone, total and free thyroxine and triiodothyronine were determined by enzyme immunoassay. Results: We observed that the high single exposure dose of sodium metavanadate caused significant changes in thyroid hormone levels. Administration of sodium metavanadate at the dose of 11 mg/kg b.w. induced an increase in the levels of total and free thyroxine but a decrease in the ratio of total triiodothyronine to total thyroxine compared with the controls. Administration of a higher dose of the compound (18 mg/kg b.w.) increased the levels of free triiodothyronine, free thyroxine, the ratio of free triiodothyronine to total triiodothyronine, and the ratio of free thyroxine to total thyroxine compared with the controls. We also noted the differences in health effects between the exposure groups, such as a higher level of free triiodothyronine and higher ratios of free triiodothyronine to total triiodothyronine and of free thyroxine to total thyroxine in the V11 exposure group. Conclusions: Our findings show that a single intraperitoneal injection of sodium metavanadate at high doses of 11 and 18 mg/kg b.w. suppresses thyroid function and induces hypothyroidism, even 14 days after administration.