Submitted to: Journal Of Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 20, 1996
Publication Date: N/A
Interpretive Summary: In mammals it is well-documented that a group of anabolic hormones, the insulin-like growth factors, have a role in fetal development. It is unknown whether a similar situation exists in the developing turkey embryos. Factors regulating the differentiation and development of the turkey embryo are poorly understood. In this study tissue and blood concentrations of insulin-like growth factor I were determined in various tissues of the turkey embryo during incubation. It was determined that IGF-I is detectable in all stages of development in most all tissues sampled. This suggests that IGF-I gene expression occurs very early in embryonic development, and that IGF-I has a significant role in turkey embryo development. This study would be of interest to other scientists in this area.
Technical Abstract: Embryonic and extra-embryonic tissue concentrations of insulin-like growth factor-I (IGF-I) were determined in the developing turkey embryo. At two day intervals, starting on Day 6 of incubation, individual tissues were and extracted in 1.0 M acetic acid for IGF- I determination. Serum, amniotic and allantoic fluid IGF-I concentrations were also determined. Serum IGF-I levels were the lowest on Days 14 and 28 of incubation (6.4 and 9.6 ng/ml) respectively, and the highest on day 20 (16.2 ng/ml). Allantoic and amniotic fluid IGF-I concentrations were essentially unchanged during incubation (2.1 to 4.0 ng/ml). Extra-embryonic tissue IGF-I levels increased in both the yolk sac and chorioallantoic membranes as incubation advanced with concentrations being 5 times greater in the chorioallantois. Embryonic tissue IGF-I concentrations varied greatly with regards to tissue and stage of development. Brain IGF-I levels were the highest on Day 8 to 10 and lowest on Day 26 (600 vs 200 pg/mg protein, respectively). Liver IGF-I was low (<150 pg/mg protein) from Day 10 to 22 and undetectable on Days 24 to 28. Muscle IGF-I ranged from 400 in early incubation to over 700 pg/mg protein in late incubation. Conversely, bone levels were highest in early embryogenesis (Day 10) and lowest on Day 28. IGF- I pattern in the heart and gastrointestinal (GI) tract mirrored serum levels in that levels peaked in mid-incubation then declined. It is apparent that tissue synthesis of IGF-I is differentially regulated within a given tissue and stage of incubation during embryogenesis in the turkey embryo.