The principal objective of this study was to examine the GH-dependency of IGF-I and IGF-II changes in the chicken.
To this end, the regulation of GH-dependent hormones and enzymes were studied in undernourished normal and dwarf chickens.
The dwarf chickens examined exhibit a Laron-type dwarfism and have been shown to be GH receptor deficient.
Thus, they provide an interesting model to determine the GH-dependency of IGF-I and IGF-II changes.
Short (1 day) and long-term (7 days) feed restriction was imposed on growing normal and dwarf chickens to follow the subsequent endocrine changes.
Since short-term feed restriction of dwarf chickens resulted in decreased plasma IGF-I, it appears that this is not a GH-dependent effect.
However, with longer term undernutrition, IGF-I was not decreased in dwarf chickens. So, after a longer restriction period, the regulation of these factors appears to become more GH-dependent.
IGF-II was not depressed at all by feed restriction in the dwarf chicken, suggesting a degree of GH-dependency.