Developmental expression of hepatic growth hormone receptor and insulin-like growth factor-I mRNA in the chicken.
We have examined the ontogeny of expression of growth hormone (GH) receptor (GHR) and insulin-like growth factor-I (IGF-I) mRNA in chicken liver from day 13 of incubation until 31 weeks of age. The profiles of GHR and IGF-I mRNA levels were compared to developmental changes in body weight and plasma levels of GH and IGF-I. In the embryo, hepatic GHR mRNA was not detectable until day 15, highest on days 17 and 19, and then declined at hatching (day 21). Following an initial 2-week delay after hatching, there was a progressive increase in hepatic GHR mRNA which continued after the birds reached mature body weight. Plasma GH reached peak levels at 3-4 weeks of age and then fell sharply until maintenance of a low basal level after 10 weeks of age. Thus, there appears to be a strong inverse relationship between expression of the GHR and basal plasma GH levels in the prepubertal chicken. Although IGF-I mRNA was undetectable in embryonic liver by Northern blot analysis, there is a good correlation between expression of hepatic IGF-I mRNA and the plasma IGF-I profile during post-hatching development in the chicken. The highest levels of IGF-I mRNA were reached at 4 weeks of age which was followed by a slow decline to the basal levels maintained after 10 weeks of age. It appears that the decline in plasma IGF-I lags considerably behind the sharp fall in plasma GH levels and expression of hepatic IGF-I mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)
Burnside
J
J
Department of Animal Science and Agricultural Biochemistry, College of Agricultural Sciences, University of Delaware, Newark 19717.
Cogburn
L A
LA
D000818:Animals; D001835:Body Weight; D002642:Chick Embryo / Q000378:metabolism*; D002645:Chickens / Q000254:growth & development / Q000378:metabolism*; D013006:Growth Hormone / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D008099:Liver / Q000196:embryology / Q000254:growth & development / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D011986:Receptors, Somatotropin / Q000096:biosynthesis* / Q000235:genetics
D012333:RNA, Messenger; D011986:Receptors, Somatotropin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone