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细胞的作用可能依赖于酪氨酸酶的活性，因为酪氨酸酶在黑色素合成过程中产生黑色素前体和自由基。我们比较了L-多巴和氧对色素沉着和无色素沉着RPE细胞生长、超氧化物歧化酶（SOD）活性和细胞周期的影响。通过改变氧浓度（20%、10%和5%），对暴露于L-dopa（100 μ M和250 μ M）的RPE细胞进行细胞计数、SOD活性和流式细胞术DNA分析。黑色素性RPE细胞比无色素性RPE细胞更耐受多巴氧化的毒性。多巴可使RPE细胞SOD活性升高，与黑色素颗粒无关。L-dopa对色素性RPE细胞的S期阻滞作用比无色素性RPE细胞更为明显，且呈剂量依赖性，氧可使细胞阻滞于G_1期。

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.