دور بعض مضادات الأكسدة الطبيعية للحد من تأثير الكادميوم على الغدة الدرقية

                "ROLE OF SOME NATURAL ANTIOXIDANTS AGAINST EFFECT OF CADMIUM IN THYROID GLAND

أميمة كامل رضوان أبو زيد""

Humans interact with their environments on a daily basis and, as a consequence, are exposed to a broad spectrum of pollutants. Among these pollutants Cd is considered one of the most toxic substances in the environment due to its wide range of organ toxicity and long elimination half-life amounted to 20-30 years. Cd causes poisoning in various tissues of humans and animals especially liver, thyroid, kidney and brain.

Thyroid hormones are associated with the oxidation status of the organism. Since data on the oxidative status of subjects with hypothyroidism are limited, this study was designed to investigate the oxidant and antioxidant status in cadmium-induced hypothyroidism and to examine the effect of some natural antioxidants (vitamins E & C and taurine) supplementation on this experimental model which comprised two separate experiments. The first one was designed to study the possible protective effect of the tested antioxidants against cadmium toxicity in plasma, liver and thyroid tissues of adult female albino rats. The second experiment was designed to investigate the possible curative effect of the tested antioxidants on Cd intoxicated rats.

The results showed that:

1)            Malondialdehyde (MDA) in plasma, liver and thyroid tissues were increased by Cd administration due to the induction of ROS in these tissues showing a state of oxidative stress.

2)            Reduced glutathione (GSH) and superoxide dismutase (SOD) levels in plasma, liver and thyroid tissues were decreased by Cd toxicity, inducing a state of oxidative stress.

3)            Oxidative stress affect the thyroid function in which the level of plasma T3 was significantly decreased, while the level of T4 showed a slight decline while a slight increase of TSH level was induced by Cd toxicity, showing a state of hypothyroidism.

4)            Cd showed significant effects on the level of T3 rather than T4, suggesting that Cd interferes with thyroid function at the extrathyroidal levels more than the thyroidal organ itself.

5)            Supplementation with vitamin E & C and taurine either prophylactic or treatment, could ameliorate and restore lipid peroxide concentration as well as the enzymatic and non-enzymatic components of antioxidant defense system in plasma, liver and thyroid tissues against Cd toxicity.

6)            The ameliorative effect of vitamin E & C and taurine supplementation improved the thyroid dysfunction by showing a gradual increase in the level of plasma T3, T4. However, the level of TSH activity was decreased in corresponding to the levels in Cd treated rats.

7)            The reinforcing capacity of vitamin E & C combination demonstrated the   complementary outputs of these two vitamins against Cd toxicity.

8)            The ameliorative effect of taurine supplementation was similar and equivalent to the protective effect produced by vitamin E&C. 

9)            The histopathological examination of Cd intoxicated thyroid gland confirmed the biochemical changes, offering deleterious changes in the thyroid tissue, showing Ultimobranchial cyst of desquamated cells in the lumen of some follicles with flattened lining epithelium.

10)         Administration of vitamin E & C, taurine showed improvement and normal appearance in thyroid tissue, characterized by empty follicular lumen with cuboidal lining epithelium."