INSULIN AND IGFS INDUCE APOPTOSIS IN CHICK-EMBRYO RETINAS DEPRIVED OFL-GLUTAMINE

In chick embryo retinas, cultured in serum-free medium lacking L gluta mine, IGF-I, IGF-II and insulin induced apoptotic DNA fragmentation an d cell death, IGF-I being the most efficacious compound. The apoptotic effect, which was particularly evident in retinas removed from 7-day old chick embryos, declined with the age of the embryos and disappeare d after day 11. Apoptosis appeared after a time lag of 8 h and then in creased with time up to 16 h, Cycloheximide, an inhibitor of protein s ynthesis, was capable of entirely abolishing apoptotic cell death. The effect induced by IGFs or insulin was suppressed by the addition of g lutamine. Cytokine mediated apoptosis was also observed after withdraw al of phosphate. We suggest that IGFs or insulin may produce, in retin as cultured in medium lacking L-glutamine or phosphate, a conflict of signals that could be lethal for retinal cells.