Effect of triiodothyronine supplementation on thyrotropin-releasing hormone-induced growth hormone secretion in sex-linked dwarf and normal chicks.
The effect of a dietary triiodothyronine (T3) supplement, of either 0.1 or 0.5 microgram/g of feed, was studied on the thyrotropin-releasing hormone (TRH)-induced growth hormone (GH) secretion in sex-linked dwarf (dw) or normal (Dw) chicks of both sexes. In normal chicks, 0.1 microgram/g T3 decreased plasma GH levels before TRH as well as the GH increase after TRH, and 0.5 microgram/g T3 totally suppressed any response to TRH, either at 4 or at 7 weeks of age. Dwarf chicks were more sensitive to TRH than normals when receiving either 0 or 0.1 microgram/g T3; 0.5 microgram/g T3 abolished the difference between genotypes at 4 weeks of age but not so clearly at 7 weeks of age, where dwarf females showed a slight but still significant GH increase after TRH. Interactions between genotype, TRH injection, and T3 treatments were often significant at 4 weeks of age and even more at 7 weeks of age. Dwarf chicks receiving 0.1 microgram/g T3, expected to have normal plasma T3 levels, showed a higher GH response after TRH. This suggests that other hormones may be involved in the regulation of this response, particularly IGF-I, which is known to remain at a low level in T3-treated dwarf chicks.
Tixier-Boichard
M
M
Laboratoire de Génétique Factorielle, Institut National de la Recherche Agronomique, Centre de Recherches de Jouy-en-Josas, France.
Monvoisin
J L
JL
Decuypere
E
E
Huybrechts
L M
LM
Kühn
E R
ER
D000704:Analysis of Variance; D000818:Animals; D002645:Chickens; D004305:Dose-Response Relationship, Drug; D004336:Drug Antagonism; D004393:Dwarfism, Pituitary / Q000178:diet therapy* / Q000378:metabolism; D005260:Female; D013006:Growth Hormone / Q000378:metabolism*; D008297:Male; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D012737:Sex Factors; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*; D014284:Triiodothyronine / Q000494:pharmacology*; D015430:Weight Gain / Q000187:drug effects
D014284:Triiodothyronine; D013973:Thyrotropin-Releasing Hormone; D013006:Growth Hormone