Abstract
This study was conducted to evaluate the effects of single and combined deficiencies of selenium and iodine on selenoenzyme activities in sheep. Twenty-four male lambs were assigned to one of four semisynthetic diets: combined deficient A (Se-I), Se-deficient B (Se-I+), I-deficient C (Se+I-), and basal diet D (Se+I+). Thyroid hormones (T-3, T-4), thyroid stimulating hormone (TSH), and inorganic iodine (PII) were determined in plasma. Selenium and glutathione peroxidase activity (GSH-Px) were determined in erythrocytes, and tissue samples, including the thyroid, liver, kidney, and brain, were taken for selenoenzyme analysis. Plasma T-3, T-4, and TSH concentrations were similar in all groups. Type I deiodinase (ID-I) activity in liver and kidney remained unchanged in Se or I deficiency. In contrast, hepatic ID-I activity was increased by 70% in combined Se-I deficiency. Thyroidal cystolic GSH-Px (c-GSH-Px) and phospholipid GSH-Px (ph-GSH-Px) activities remained constant in both Se-deficient groups, whereas thyroidal c-GSH-Px activity increased (57%) in I deficiency. Type II deiodinase (ID-II) activity was not detectable in the cerebrum and cerebellum, whereas cerebellum Type III deiodinase (ID-III) activity was decreased in I deficiency and combined Se-I deficiencies. The results of the present study support a sensitive interaction between Se and I deficiencies in sheep thyroid and brain. Furthermore, the lack of thyroidal ID-I activity, the preservation of the thyroidal antioxidant enzymes, and the increases in hepatic ID-I indicate that a compensatory mechanism(s) works toward retaining plasma T-3 levels, mostly by de novo synthesis of T-3 and peripheral deiodination of T-4 in Se- and I-deficient sheep.
Original language | English |
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Pages (from-to) | 213-224 |
Number of pages | 12 |
Journal | Biological Trace Element Research |
Volume | 94 |
Issue number | 3 |
DOIs | |
Publication status | Published - Sep 2003 |
Keywords
- Se
- I
- selenoenzymes
- sheep
- iodothyronine deiodinase
- expression
- rats
- cattle