方法：视网膜色素上皮细胞经紫外线A照射、高渗和低渗培养后不同时间点，通过定量PCR方法测定甜菜碱/γ-氨基丁酸转运蛋白，钠依赖式肌醇转运蛋白和牛磺酸转运蛋白mRNA的表达水平，通过放射性同位素标识的渗透压小分子物质测量渗透压小分子物质在不同实验条件下的细胞内外转运过程。

结果：本研究证明视网膜色素上皮细胞表达甜菜碱/γ-氨基丁酸转运蛋白，钠依赖式肌醇转运蛋白和牛磺酸转运蛋白mRNA。高渗(400mosmol/L)相对于等渗(300mosmol/L)引发甜菜碱/γ-氨基丁酸转运蛋白、钠依赖式肌醇转运蛋白和牛磺酸转运蛋白的mRNA升高约3～5倍。高渗同时引发放射性同位素标记的渗透压小分子物质细胞内积聚。相反，低渗(200mosmol/L)引发渗透压小分子物质外流至细胞外。紫外线A照射明显引发渗透压小分子物质向细胞内摄入。与此同时，紫外线A照射还引发细胞膜相应转运蛋白的mRNA的上调。

结论：本实验表明紫外线A可以引发与高渗相类似的渗透压小分子物质的细胞内积聚效应，这种效应对保持细胞内稳态有重要作用。

METHODS: Under different experimental conditions such as UVA exposure, hyperosmotic stress condition and hypoosmotic stress condition, RPE cells were cultured for different time periods. The betaine /γ-amino- n-butyric acid(GABA)transporter, the sodium-dependent myoinositol transporter and the taurine transporter(TAUT)mRNA were measured by quantitative PCR. The radioactive labeled osmolytes were measured to evaluate the level of osmolytes transportation.

RESULTS: This study demonstrated that RPE expressed mRNA specific for the betaine/GABA transporter, for the sodium-dependent myoinositol transporter and for the TAUT. In comparison to norm osmotic(300mosmol/L)controls, a 3-5-fold induction of mRNA expression for the betaine/GABA transporter, the sodium-dependent myoinositol transporter and the TAUT was observed within 6-24h after hyperosmotic exposure(400mosmol/L). Expression of osmolyte transporters was associated with an increased uptake of radioactive labeled osmolytes. Conversely, hypoosmotic(200mosmol/L)stimulation induced significant efflux of these osmolytes. UVA significantly stimulated osmolyte uptake. Increased osmolyte uptake was associated with upregulation of mRNA steady-state levels for osmolyte transporters in irradiated cells.

CONCLUSION: UVA induces osmolyte uptake in RPE. It is similar reaction to hyperosmotic stress. This suggests that osmolyte uptake response by UVA may be important to maintain homeostasis.