CHANGES IN MYOCARDIAL THYROID-HORMONE METABOLISM AND ALPHA-GLYCEROPHOSPHATE DEHYDROGENASE-ACTIVITY IN RATS DEFICIENT IN IODINE AND SELENIUM

Weanling Wistar rats were fed on diets prepared from grain from areas deficient in I and Se where Keshan disease is endemic. Rats were divid ed into four groups, each of twelve rats, and received a diet suppleme nted with: I, Se, I+Se or nothing. At 8 weeks after weaning, myocardia l alpha-glycerophosphate dehydrogenase (EC 1.1.1.8; alpha-GPD) activit y and indices of Se and thyroid hormone status were determined. The gr oup supplemented with iodine had increased plasma thyroxine levels. Th ere was no difference in plasma triiodothyronine concentration between the groups but triiodothyronine levels in heart were reduced in the S e-supplemented group. Se supplementation increased myocardial glutathi one peroxidase activity (EC 1.11.1.9) and the type I 5'-deiodinase (EC 3.8.1.4) activity in rat liver, but no type I 5'-deiodinase activity was detected in heart. alpha-GDP activity in heart was increased in th e group supplemented with Se, I or both. There was a significant relat ionship (P < 0.05) between myocardial alpha-GDP activity and plasma th yroxine levels but not between alpha-GDP and myocardial glutathione pe roxidase activity. The results indicate that iodine may be more import ant than Se in energy metabolism in the myocardium, which may give a n ew insight for the study of the aetiology of Keshan disease in areas w here foodstuffs are deficient in both Se and I.