Growth hormone-independent expression of insulin-like growth factor I messenger ribonucleic acid in extrahepatic tissues of the chicken.
The sex-linked dwarf (SLD) chicken, which lacks GH receptor (GHR), and its normal littermates provide a useful experimental system to investigate GH-dependent cellular responses. The GH dependence of insulin-like growth factor I (IGF-I) expression in tissues was examined in SLD and normal chickens of the Gifu 20 strain. Four weeks after hatching, the most abundant expression of IGF-I messenger RNA (mRNA) was observed in liver of normal chickens, whereas no IGF-mRNA expression was detected in that organ of dwarf chickens. On the contrary, in extrahepatic tissues such as spleen, lung, brain, kidney, heart, intestine, thymus, and muscle, IGF-I mRNA expression was equally observed in normal and GHR-lacking dwarf chickens. In the testis, expression of IGF-I mRNA was enhanced by about 5-fold in dwarf chickens showing an expression level comparable to that in normal liver. On day 16 in the embryonic stage, IGF-I mRNA was expressed in muscle, brain, eye, heart, and lung in both normal and SLD chick embryos. However, no IGF-I mRNA expression was observed in liver or kidney of normal and dwarf chick embryos. These results suggest that in chicken, IGF-I mRNA is expressed in liver in a GH-dependent manner after hatching, whereas in other tissues, mRNA expression is independent of GH and GHR before and after hatching, except for testis, in which GH seems to inhibit IGF-I mRNA expression.
Department of Biochemistry, Faculty of Medicine, Mie University, Japan.
M
M
Tanaka
Y
Y
Hayashida
K
K
Sakaguchi
T
T
Ohkubo
M
M
Wakita
S
S
Hoshino
K
K
Nakashima
D000818:Animals; D015152:Blotting, Northern; D002645:Chickens / Q000378:metabolism*; D004392:Dwarfism / Q000235:genetics / Q000378:metabolism; D013006:Growth Hormone / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D008099:Liver / Q000378:metabolism*; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000378:metabolism*; D012016:Reference Values; D012260:Ribonucleases
D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D012260:Ribonucleases