Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 12, 2005
Publication Date: January 14, 2005
Citation: Karcher, D.M., McMurtry, J.P., Applegate, T.J. 2005. Developmental changes in amniotic and allantoic fluid insulin-like growth factor (IGF) - I and -II concentrations of avian embryos. Comparative Biochemistry and Physiology Part A. 142:404-409.
Interpretive Summary: The insulin-like growth factors I and II are ubiquitous peptide hormones known to have potent effects on organismal growth and development. Both growth factors are produced in most all tissues. It is well-documented that the growth factors play an important role during avian embryonic development. Most of this information comes from research on the chick embryo. During embryonic development, the developing embryo swallows amniotic fluid, which contains proteins, minerals, water and other nutrients. Previous work in mammalian fetuses has reported that mammalian amniotic fluid contains significant amounts of growth factors, and that these factors are important to gastrointestinal development. The study described herein was conducted to determine whether the insulin-like growth factors are present in amniotic and allantoic fluids of the duck, chicken and turkey embryos during incubation. In summary, it was determined that growth factors are present in both embryonic fluids in all three species, and that concentrations vary depending on the stage of incubation. The results suggest that growth factors present in these extraembryonic fluids may contribute to embryo development; however, to what extent, remains to be determined. These results will be of interest to other scientists.
Fluctuating concentrations of IGF in the developing embryo have been reported in the literature, however, the majority are based upon blood serum concentrations. Therefore, this project quantified the presence and abundance of IGF-I/-II within the amniotic and allantoic fluids during development of the chicken, duck, and turkey. For this study, fertile commercial broiler (n = 222), Pekin duck (n = 250), and turkey eggs (n = 200) were obtained and incubated. Amniotic and allantoic fluids were collected from embryos starting at 6 days of incubation for chickens and 8 days of incubation for ducks and turkeys. IGF-I and -II concentrations within the fluids were determined by radioimmunoassay. Chicken amniotic IGF-I concentration at stage 29 of development (wing bent at the elbow on the embryo and presence of a prominent beak) was significantly higher (P < 0.05) than the duck or turkey. At stage 36 of development (tapering of the claws and the lower lid of the eye grown upward to be level with the cornea) the concentration of IGF- II in the amniotic fluid was 2.8 times greater in the chicken versus the duck (P < 0.05) and 2 times greater than the turkey (P < 0.05). Within species, chicken IGF-I concentration in the amniotic fluid had a cubic response (P < 0.001), duck IGF-I increased linearly (P < 0.001), and turkey concentrations declined quadratically (P < 0.001) throughout development. In all species, the IGF-II concentration was higher than the IGF-I concentration in the amniotic and allantoic fluids.