Effects on Retinal Pigment Epithelium in Vitro of Dopa and Oxygen.

目的。左旋多巴和氧对视网膜色素上皮（RPE）细胞的影响可能依赖于酪氨酸酶的活性，因为酪氨酸酶在合成黑色素的过程中会产生黑色素前体和自由基。我们比较了左旋多巴和氧对黑色素RPE细胞生长、超氧化物歧化酶（SOD）活性和细胞周期的影响。我们对暴露于L-dopa（100和250 muM）改变氧浓度（20%，10%和5%）的RPE细胞进行了细胞计数，SOD活性和流式细胞术DNA分析。黑色RPE细胞比无色RPE细胞更能耐受多巴氧化的毒性。不论是否有黑色素颗粒，多巴均可提高RPE细胞的SOD活性。L-dopa对细胞周期（S期）的阻滞作用在黑化RPE细胞中比在无色化RPE细胞中更为明显，氧在G_1期引起阻滞。

Purpose. It is possible that the effects of L-dopa and oxygen on retinal pigment epithelial (RPE) cells are dependent on tyrosinase activities because melanin precursors and free radicals are produced during melanin synthesis by tyrosinase. We compared these cytotoxic effects of L-dopa and oxygen on cell growth, superoxide dismutase (SOD) activity, and cell cycle of melanotic RPE cells with amelanotic RPE cells.Methods. We conducted cell count, SOD activity, and flow cytometric DNA analysis of RPE cells exposed to L-dopa (100 muM and 250 muM) changing oxygen concentrations (20%, 10%, and 5%).Results. Melanotic RPE cells were more tolerant of toxicity of dopa-oxidation than amelanotic RPE cells. SOD activity of RPE cells was increased by exposure to dopa regardless of melanin granules. A dose-dependent effect of L-dopa to arrest the cell cycle (the S phase) was more pronounced in melanotic RPE cells than in amelanotic RPE cells, and oxygen caused arrest in the G_1 phase.