Simulation of the conditions of gyrate atrophy in vitro suppresses retinal protein synthesis.

The effect of ornithine on retinal protein synthesis was evaluated using isolated baboon retinas maintained in vitro. When ornithine was present in the culture medium at a concentration equivalent to the plasma level of ornithine in gyrate atrophy patients (1 mM), the incorporation of 3H-leucine was reduced to 70 per cent of control levels. Progressively higher concentrations of ornithine resulted in a further suppression of protein synthesis. Soluble radioactivities after short incubation times from control and ornithine cultured retina were similar indicating no effect of ornithine on uptake of 3H-leucine. Grain counts in autoradiographs of control and ornithine-treated retinas revealed a suppression of incorporation in all retinal strata. These results suggest that elevated ornithine levels may suppress ongoing protein synthesis in the retina.