Changes of iodothyronine levels in plasma after acute and long term hypokinesia (unforced restriction) in rats.
Groups of 8 rats each were subjected to hypokinesia (unforced restriction) in plexiglass cages for 1, 5 and 9 days in first experiment and groups of 10 rats each were subjected to 1, 5, 14 and 60 days of hypokinesia in a second experiment. In addition, in a second experiment two groups of 10 animals were subjected first to hypokinesia for 60 days and then kept in regular group cages for 7 and 21 days, respectively. In each experiment a control group was used which was not subjected to restriction. Each animal was decapitated at the appropriate interval and the level of thyroxine (T4), 3,5,3'-triiodothyronine (T3) and 3,3',5'-triiodothyronine (rT3) was measured with the aid of radioimmunoassay. Most remarkable changes appeared on the first day of hypokinesia when significantly increased levels of TR and T3 were found in both experiments. In a second experiment the level of T4 was significantly decreased in all groups but that restricted for 1 day. No changes of T3 level were found with the exception of the above described increase in the first day, while the levels of rT3 showed irregular and inconsistent changes. A hypothesis was tested whether the increased T4 and T3 levels result from a decreased fecal excretion of these compounds due to presumably increased food intake during the first day of hypokinesia, but it was found that the intake of food and water on the first day was the same as on subsequent days. Thus, the mechanism of the observed changes remains to be further studied.
D000818:Animals; D007103:Immobilization; D007700:Kinetics; D008297:Male; D051381:Rats; D013974:Thyroxine / Q000097:blood*; D014284:Triiodothyronine / Q000097:blood*; D014285:Triiodothyronine, Reverse / Q000097:blood*
D014284:Triiodothyronine; D014285:Triiodothyronine, Reverse; D013974:Thyroxine