Akeo K, Tanaka Y, Okisaka S
Department of Ophthalmology, National Defense Medical College, Saitama, Japan.
Pigment Cell Res. 1994 Jun;7(3):145-51. doi: 10.1111/j.1600-0749.1994.tb00042.x.
Melanin precursors and free radicals, cytotoxic substances, are produced during melanin synthesis by tyrosinase. We compared these cytotoxic effects of L-dopa and oxygen on the cell cycle of melanotic retinal pigment epithelial (RPE) cells with amelanotic RPE cells because of the differences of tyrosinase activities between melanotic and amelanotic RPE cells. Flow cytometric DNA analysis of RPE cells exposed to L-dopa (100 microM and 250 microM) were conducted at several oxygen concentrations (20%, 10%, and 5%). The dose-dependent effect of L-dopa to arrest the cell cycle (the S phase) was more pronounced in melanotic than in amelanotic RPE cells, and oxygen caused arrest in the G1 phase.
黑色素前体以及自由基（细胞毒性物质）是在酪氨酸酶合成黑色素的过程中产生的。由于有色素性视网膜色素上皮（RPE）细胞和无色素性RPE细胞之间酪氨酸酶活性存在差异，我们比较了左旋多巴和氧气对有色素性RPE细胞与无色素性RPE细胞细胞周期的这些细胞毒性作用。在几种氧气浓度（20%、10%和5%）下，对暴露于左旋多巴（100微摩尔和250微摩尔）的RPE细胞进行了流式细胞术DNA分析。左旋多巴使细胞周期（S期）停滞的剂量依赖性效应在有色素性RPE细胞中比在无色素性RPE细胞中更明显，而氧气导致细胞停滞在G1期。
