title: Ontogeny of the effect of purified chicken growth hormone on the liver 5' monodeiodination activity in the chicken: reversal of the activity after hatching.
abstract: The ontogeny of the effect of chicken growth hormone (c-GH) on the liver 5' monodeiodination (5'-D) activity was studied in chickens starting from 14-day-old embryos until 5-week-old chickens. Ten micrograms of the purified hormone was injected intravenously and after 2 hr, blood and liver samples were taken. In all embryonic stages tested, c-GH stimulated the peripheral thyroxine (T4) to triiodothyronine (T3) conversion as demonstrated by the increased plasma T3 level and liver 5'-D activity while the plasma reverse T3 (rT3) level was decreased. In chicks 1 day after hatching, GH was still able to increase the plasma T3 level and the liver 5'-D activity. However, in 2-day-old chicks, this stimulation had completely disappeared, while the control value of the plasma T3/T4 ratio was considerably higher than the day before. The effect of c-GH injection gradually turned into a decrease of 5'-D activity and plasma T3 in 5- and 7-day-old chicks. Further on, no effect of c-GH could be found in 2- to 4-week-old growing chickens, but in 5-week-old GH-injected animals the plasma T4 and rT3 level decreased again, although no significant effect on T3 or liver 5'-D activity could be demonstrated.
authors.affiliation: Laboratory of Comparative Endocrinology, K.U.L., Leuven, Belgium.
authors.forename: V M
authors.initials: VM
authors.lastname: Darras
authors.forename: L M
authors.initials: LM
authors.lastname: Huybrechts
authors.forename: L
authors.initials: L
authors.lastname: Berghman
authors.forename: E R
authors.initials: ER
authors.lastname: Kühn
authors.forename: E
authors.initials: E
authors.lastname: Decuypere
mesh_terms: D000818:Animals; D002642:Chick Embryo / Q000378:metabolism*; D002645:Chickens / Q000378:metabolism*; D013006:Growth Hormone / Q000494:pharmacology*; D007453:Iodide Peroxidase / Q000378:metabolism*; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D013963:Thyroid Hormones / Q000097:blood* / Q000378:metabolism; D013974:Thyroxine / Q000097:blood / Q000378:metabolism; D014284:Triiodothyronine / Q000097:blood / Q000378:metabolism; D014285:Triiodothyronine, Reverse / Q000097:blood / Q000378:metabolism
chemical_list: D013963:Thyroid Hormones; D014284:Triiodothyronine; D014285:Triiodothyronine, Reverse; D013006:Growth Hormone; D007453:Iodide Peroxidase; D013974:Thyroxine