[Electron microscopic studies of retinal pigment epithelial cells incubated with L-dopa in 10% and 20% oxygen]

In order to make clear how the ultrastructure of the bovine second-passage retinal pigment epithelium (RPE) was affected by exposure to L-dopa and oxygen, we compared the toxic effects of melanotic and amelanotic RPE. The oxygen levels in the incubators and the L-dopa concentrations in the media were adjusted to 10% or 20% oxygen by adding nitrogen gas and 100 microM or 250 microM L-dopa, respectively. After 24 hours, melanotic and amelanotic RPE were fixed and embedded in epon. Ultrathin sections were examined by transmission electron microscopy. Rough endoplasmic reticula were found to be dilated and ribosomes were extinguished in both melanotic and amelanotic RPE. The damage by L-dopa in melanotic RPE was less than that in amelanotic RPE and less in 10% oxygen than in 20% oxygen.