SELENIUM DEFICIENCY ALTERS THYROID-HORMONE METABOLISM IN GUINEA-PIGS

In guinea pigs, activity of glutathione peroxidase in most organs is m arkedly lower than in organs of other rodents despite comparable dieta ry intakes and tissue levels of selenium. To determine if metabolism o f selenium with respect to other selenoproteins also differs in guinea pigs, we measured the effects of selenium intake on thyroid hormone m etabolism. Weanling male Hartley Albino guinea pigs were fed a seleniu m-deficient Torula yeast-based diet, or the same diet supplemented wit h 0.5 mg selenium/kg diet as sodium selenate for 72 d. Growth was impa ired in guinea pigs fed the unsupplemented diet. Activity of glutathio ne peroxidase was higher in tissues and plasma of supplemented guinea pigs than in selenium-deficient animals. However, it was still far low er than reported values for other rodent species. In selenium deficien cy, activity of type 1 5'-iodothyronine deiodinase was 60% less in liv er and 45% less in kidney. Concentration of thyroxine was 68% lower in kidney of selenium-deficient animals, and levels of 3,3',5-triiodothy ronine in kidney and plasma were 44 and 31% lower, respectively. Thus, with the exception of thyroxine concentrations, thyroid hormone metab olism responds to selenium deficiency in guinea pigs as it does in rat s, although the magnitude of that response is not as great.