CHICK-EMBRYO RETINA DEVELOPMENT IN-VITRO - THE EFFECT OF INSULIN

In this paper we study the development of chick embryo retina cultured in vitro and the effects exerted by insulin. Retinas were removed fro m 7-day embryos and cultured in serum-and hormone- free medium for 7 a dditional days. Under these conditions retinal cells survived and unde rwent cholinergic differentiation, as previously ascertained by Hausma n et al. (Dev. Brain Res., 1991, 59:31-37). However, a great retardati on of development was noted compared to uncultured control, 14-day ret ina. In fact both wet weight and DNA and protein content increased muc h slower than in ovo and the tubulin content decreased below even the starting value. In addition, although after 7 days in culture retinal cells were organized in identifiable layers, nevertheless the typical organization equivalent to 14-day in ovo retina was absent. The additi on of insulin in the medium markedly increased the wet weight of cultu red retinas, their protein content and the level of tubulin pools, par ticularly that of non-assembled fraction. Nevertheless insulin did not modify DNA synthesis and did not induce the increment of both neuron specific enolase and actin. Morphological observations show that insul in markedly increased the number and the thickening of the fiber layer s. These results, together with the facts that retina synthesizes and secretes insulin and possesses specific insulin receptors suggest that insulin can have autocrine or paracrine regulatory functions in retin al development by exerting a general effect on retinal growth and a mo re specific one on tubulin production.