Stress is associated with inhibition of type I iodothyronine 5'-deiodinase activity in rat liver.
Type I iodothyronine deiodinase (5'-DI) generates the thyromimetically active hormone 3,5,3'-triiodothyronine (T(3)) by reductive monodeiodination of the phenolic ring of L-thyroxine (T(4)). The present study was undertaken to compare the effects of cold stress (4 degrees C) alone or in combination with immobilization stress (IMO), insulin treatment (5 IU/kg, i.p.) or 2-deoxy-D-glucose (2DG)-induced intracellular glucopenia on the activity of 5'-DI in rat liver. Cold stress either for 24 h or 28 days when compared to that in the nonstressed group of rats significantly reduced (P < 0.001) the activity of 5'-DI in liver. In comparison with cold stressed rats for 28 days, an additional decrease in 5'-DI activity was observed when those rats underwent 1 x IMO in cold for 2 h (P < 0.001) or insulin treatment (P < 0.05). A significant decrease in 5'-DI activity was found also in rats maintained at room temperature that underwent a single 1 x IMO for 2 h (P < 0.001) or insulin treatment (P < 0.01) when compared to nonstressed animals. In comparison with nonstressed rats, no significant change of the 5'-DI activity was observed after 2DG application (500 mg/kg, i.p.) at room temperature. In conclusion, cold stress and/or 1 x IMO, insulin treatment, or 1 x IMO at room temperature markedly affects reductive monodeiodination of T(4), and thus reduces the concentration of biologically active T(3) in liver.
Brtko
Július
J
D.Sc., Institute of Experimental Endocrinology, Slovak Academy of Sciences, Vlárska 3, 833 06 Bratislava, Slovak Republic. julius.brtko@savba.sk
Macejová
Dana
D
Knopp
Ján
J
Kvetnanský
Richard
R
D000818:Animals; D003847:Deoxyglucose / Q000494:pharmacology; D007103:Immobilization; D007453:Iodide Peroxidase / Q000037:antagonists & inhibitors*; D008099:Liver / Q000201:enzymology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013312:Stress, Physiological / Q000201:enzymology*
D003847:Deoxyglucose; D007453:Iodide Peroxidase