Premium
Growth hormone acutely decreases type III iodothyronine deiodinase in chicken liver
Author(s) -
Darras V.M.,
Berghman L.R.,
Vanderpooten A.,
Kühn E.R.
Publication year - 1992
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(92)81133-7
Subject(s) - iodothyronine deiodinase , deiodinase , dio2 , medicine , endocrinology , hormone , chemistry , growth hormone , thyroid hormones , biology
Growth hormone (GH) increases plasma T 3 and decreases plasma T 4 in 18‐day old chicken embryos, in newly hatched chicks and in adult chickens within 2 h after injection. The in vivo increase in T 3 can be linked to an increased in vitro T 3 recovery from liver homogenates incubated with T 4 . Specific type I and type III deiodinase tests (5′D‐I and 5D‐III), however, show that GH has no effect at all on the amount of hepatic type I enzyme (catalyzing T 4 deiodination to T 3 ) but acutely decreases the amount of type III enzyme (catalyzing T 3 deiodination). This suggests that the GH‐induced increase in plasma T 3 is not due to an increased T 3 production, but is the result of a decreased T 3 breakdown. The lack of a stimulatory effect of GH injection in 3‐day‐old fed chicks might be the combined result of a low hepatic type III enzyme level and a low GH receptor availability at that stage.