Toxicological Effects of Toxic Metals (Cadmium and Mercury) on Blood and the Thyroid Gland and Pharmacological Intervention by Vitamin C in Rabbits

Environ Sci Pollut Res Int. 2019 Jun;26(16):16727-16741. doi: 10.1007/s11356-019-04886-9. Epub 2019 Apr 16.

Abstract

Cadmium and mercury are non-biodegradable toxic metals that may cause many detrimental effects to the thyroid gland and blood. Vitamin C has been found to be a significant chain-breaking antioxidant and enzyme co-factor against metal toxicity and thus make them less available for animals. The current study was performed to find the effect of individual metals (cadmium and mercury), their co-administration, and the ameliorative effects of vitamin C on some of the parameters that indicate oxidative stress and thyroid dysfunction. Cadmium chloride (1.5 mg/kg), mercuric chloride (1.2 mg/kg), and vitamin C (150 mg/kg of body weight) were orally administered to eight treatment groups of the rabbits (1. control; 2. Vit C; 3. CdCl2; 4. HgCl2; 5. Vit C + CdCl2; 6. Vit C + HgCl2; 7. CdCl2 + HgCl2, and 8. Vit C + CdCl2 + HgCl2). After the biometric measurements of all experimental rabbits, biochemical parameters viz. triidothyronine (T3), thyroxine (T4), thyroid-stimulating hormone (TSH), and triglycerides were measured using commercially available kits. The results exhibited significant decline (p < 0.05) in mean hemoglobin, corpuscular hemoglobin, packed cell volume, T3 (0.4 ± 0.0 ng/ml), and T4 (26.3 ± 1.6 ng/ml) concentration. While, TSH (0.23 ± 0.01 nmol/l) and triglyceride (4.42 ± 0.18 nmol/l) were significantly (p < 0.05) increased but chemo-treatment with Vit C reduces the effects of Cd, Hg, and their co-administration but not regained the values similar to those of controls. This indicates that Vit C had a shielding effect on the possible metal toxicity. The Cd and Hg also found to accumulate in vital organs when measured by atomic absorption spectrophotometer. The metal concentration trend was observed as follows: kidney > liver > heart > lungs. It was concluded that Cd and Hg are toxic and tended to bioaccumulate in different organs and their toxic action can be subdued by vitamin C in biological systems.

Keywords: Antioxidants; Bioaccumulation; Thyroid; Toxic metals; Trace elements.

MeSH terms

  • Animals
  • Antioxidants / pharmacology*
  • Ascorbic Acid / pharmacology*
  • Body Weight / drug effects
  • Cadmium / metabolism
  • Cadmium / toxicity*
  • Heavy Metal Poisoning
  • Hemoglobins / analysis
  • Kidney / drug effects
  • Kidney / metabolism
  • Liver / drug effects
  • Liver / metabolism
  • Mercury / metabolism
  • Mercury / toxicity*
  • Oxidative Stress / drug effects
  • Rabbits
  • Thyroid Gland / drug effects*
  • Thyroid Gland / metabolism
  • Thyroid Hormones / blood*
  • Thyrotropin / blood*

Substances

  • Antioxidants
  • Hemoglobins
  • Thyroid Hormones
  • Cadmium
  • Thyrotropin
  • Mercury
  • Ascorbic Acid