APOPTOSIS IN THE DEVELOPING RETINA - PARADOXICAL EFFECTS OF PROTEIN-SYNTHESIS INHIBITION

Cell death by apoptosis is usually characterized as an active process that requires protein and RNA synthesis. The requirement of protein sy nthesis for the degeneration of ganglion cells and other cell types wa s studied in neural retinae explanted from the eyes of newborn rats. G anglion cells were detected by the presence of retrogradely transporte d horseradish peroxidase injected into the superior colliculus. Apopto tic cells were recognized by their condensed and deeply stained chroma tin. The data show that the death of ganglion cells, whose axons are d amaged when preparing the explants, is blocked or delayed by protein s ynthesis inhibitors. In contrast, the blockade of protein synthesis pr oduced cell death with apoptotic morphology in the neuroblastic layer of the same retinae. The results suggest the operation in the developi ng retina of both a program of apoptosis dependent on the synthesis of killer proteins, and a latent mechanism of apoptosis that is normally blocked by repressor proteins.