CHANGES OF IODOTHYRONINE LEVELS IN PLASMA AFTER ACUTE AND LONG-TERM HYPOKINESIA (UNFORCED RESTRICTION) IN RATS

  • 1 January 1981
    • journal article
    • research article
    • Vol. 15  (2) , 139-144
Abstract
Groups of 8 rats each were subjected to hypokinesia (unforced restriction) in plexiglass cages for 1, 5 and 9 days in the 1st experiment and groups of 10 rats each were subjected to 1, 5, 14 and 60 days of hypokinesia in a 2nd experiment. In a 2nd experiment 2 groups of 10 animals were subjected 1st 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 1st day of hypokinesia when significantly increased levels of T4 and T3 were found in both experiments. In a 2nd 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 on the 1st day, while the levels of rT3 showed irregular and unconsistent 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 1st day of hypokinesia, but it was found that the intake of food and water on the 1st day was the same as on subsequent days. The mechanism of the observed changes remains to be further studied.