[Phenylalanine-influenced retinal changes in the newborn rat (author's transl)].

Subject of the present study was the retina of rats following intravenous application of L-phenylalanin. The 19 newborn rats received 0.9 mg/g of the substance twice daily from the first to the seventh postnatal day. Depending on the survival time, alterations of ganglion cells, neuropil, and capillaries were found. Pyknotic and necrotic cells in the bipolar and in the ganglion layer occurred. Animals that were treated for a period of five days developed a marked increase of free ribosomes and round particles with a granular matrix of the cytoplasma but without membranes. Also suggesting damage is the increase of the glycogen in the bipolar and the inner granular layer as well as in the nerve cell extensions adjacent to the capillaries. An additional finding is the swelling of processes of the glia and of neuronal cells in the vicinity of the retina vessels. Since newborn rats do not have the blood-brain carrier of adult animals, toxic damage of the cell membranes with intracellular liquid accumulation can be concluded. Our findings suggest that L-phenylalanin can damage the nerve cell substantially and that alterations of the white matter so far described are not the sole basis of phenylketonuria.