Growth and plasma triiodothyronine concentrations are modified by selenium deficiency and repletion in second-generation selenium-deficient rats.
Classical glutathione peroxidase (GPX) is a useful Se-dependent parameter for determining Se status, but loss of GPX activity alone cannot explain the full effects of Se deficiency. The recent identification of type I thyroxine 5'-deiodinase as a Se-dependent enzyme provides a new potentially critical role for Se. To develop a model of impaired growth due to Se deficiency, second generation deficient weanling rats were fed a Se-deficient amino acid diet with adequate vitamin E and methionine. Initial growth rates of deficient males and females were 53 and 63%, respectively, of rats fed 0.1 micrograms Se/g diet. In short-term experiments with deficient males, liver Se and GPX activity were reduced 99%, liver glutathione-s-transferase activity was increased 114%, plasma thyroxine concentrations were increased 67%, plasma triiodothyronine was decreased 23% and the plasma triiodothyronine:thyroxine ratio was decreased 55%, compared with rats fed 0.2 micrograms Se/g diet. When deficient rats were injected on d 14 with 0, 1, 5 or 10 micrograms Se/100 g, rats grew 4.45, 7.62, 7.17 and 9.05 g/d, respectively, over the next 7 d. Injection with 10 micrograms Se/100 g restored plasma thyroxine and triiodothyronine concentrations 7 d later. Rats injected with 1 microgram Se/100 g rat had significantly altered plasma thyroxine and triiodothyronine concentrations 1 but not 7 d after injection. Infusion of Se-deficient rats with 438 ng triiodothyronine/d for 7 d restored plasma triiodothyronine concentrations but did not increase growth rate compared with rats infused with saline. This model produced a significant growth depression that was significantly reversed by as little as 1 microgram Se/100 g rat, but not by triiodothyronine infusion, suggesting that other Se-dependent roles in addition to 5'-deiodinase and GPX are necessary for adequate growth.
Thompson
K M
KM
Nutritional Sciences Group, University of Missouri, Columbia 65211, USA.
Haibach
H
H
Sunde
R A
RA
D000818:Animals; D004032:Diet; D005260:Female; D005979:Glutathione Peroxidase / Q000032:analysis; D005982:Glutathione Transferase / Q000032:analysis; D006128:Growth / Q000187:drug effects* / Q000502:physiology; D008099:Liver / Q000737:chemistry / Q000201:enzymology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012643:Selenium / Q000032:analysis / Q000172:deficiency* / Q000494:pharmacology*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood*
D014284:Triiodothyronine; D005979:Glutathione Peroxidase; D005982:Glutathione Transferase; D012643:Selenium; D013974:Thyroxine