Changes in myocardial thyroid hormone metabolism and α-glycerophosphate dehydrogenase activity in rats deficient in iodine and selenium

Abstract

Weanling Wistar rats were fed on diets prepared from grain from areas deficient in I and Se where Keshan disease is endemic. Rats were divided into four groups, each of twelve rats, and received a diet supplemented with: I, Se, I + Se or nothing. At 8 weeks after weaning, myocardial α-glycerophosphate dehydrogenase (EC1.1.1.8; α-GPD) activity and indices of Se and thyroid hormone status were determined. The group supplemented with iodine had increased plasma thyroxine levels. There was no difference in plasma triiodothyronine concentration between the groups but triiodothyronine levels in heart were reduced in the Se-supplemented group. Se supplementation increased myocardial glutathione peroxidase activity (EC1.11.1.9) and the type I 5'-deiodinase (EC3.8.1.4) activity in rat liver, but no type I 5'-deiodinase activity was detected in heart. α-GDP activity in heart was increased in the group supplemented with Se, I or both. There was a significant relationship (P< 0.05) between myocardial α-GDP activity and plasma thyroxine levels but not between α-GDP and myocardial glutathione peroxidase activity. The results indicate that iodine may be more important than Se in energy metabolism in the myocardium, which may give a new insight for the study of the aetiology of Keshan disease in areas where foodstuffs are deficient in both Se and I.