ABSTRACT
The chick embryo is a classical model to study eye development. As pituitary growth hormone (GH) is an established growth factor, it was tacitly assumed that it was causally involved in embryogenesis and eye growth. Ocular tissues are not just sites of GH production, as they express the GH receptor (GHR) gene and are thus sites of GH actions. In addition to the full-length GHR, other receptors may be present in the chick eye, as small-chicken GH (s-cGH) immunoneutralization inhibits retinal ganglion cell (RGC) survival in chick embryo cultures. The expression of GH mRNA in the neural retina of chick embryos is likely to be stimulated, as in the pituitary gland, by the action of GH-releasing hormone (GHRH). Pituitary GH secretion occurs in the last trimester of incubation and as it can be internalized into the RGCs of the neural retina, it may also contribute to chick eye development in late embryogenesis.
