OBJECTIVE:To observe the effect of dexamethasone to intracellular free Ca2+ of frozen RPE cells. METHODS:The cultured human RPE cells were frozen for 30s at --70deg;C. The RPE cells were loaded with Fura-2/AM and analyzed using a digital imaging microscopy system,the effect of dexamethasone to intracellular free Ca2+ was measured at a serial concentration of 40, 60,100,150,200mu;g/ml. RESULTS:The concentration of intracellular free Ca in frozen human RPE cells was increased to 18.6%~29.8% by dexamethasone at concenlration of 40mu;g/ml~60mu;g/ml,while was decreased to 28.4%~35.2% at 150mu;g/ml~200mu;g/ml. CONCLUSIONS:Effect of dexamethasone showed two aspects of effect to frozen cultured human RPE ceils,that it was inhibitor at high concentration and stimulator at low concentration （Chin J Ocul Fundus Dis,1997,13: 86-88）
Objective To investigate the role of intracellular Ca2+ and MERTK in the phagocytosis of human retinal pigment epithelial (RPE) cells, and reveal the relationship between MERTK and intracellular Ca2+. Methods The cultured RPE cells were incubated with rod outer segments (ROS) at 37℃, the phagocytosis was terminated at different incubation time points. The concentration of intracellular Ca2+ was assayed by Fluro-3/AM loading methods combined with fluorescence microscope and CCD system, and the mRNA level of MERTK gene was measured by reverse transcription polymerase chain reaction (RT-PCR). Treating the RPE cells with stimulator (A23187) or inhibitor (verapamile) of intracellular Ca2+ to observe the changes of MERTK gene expression. Results ROS adhered to hRPE cells at the 15th minute, and the ingestion saturated at the 24th hour. The concentration of intracellular Ca2+ increased at the 15th minute, and kept the high level in 24 hours. The level of MERTK mRNA increased at the 5th minute, and kept the high level duration the whole incubation. When RPE cells were treated by A23187, the expression of MERTK increased in a dose-dependent manner. After RPE cells was pretreated by A23187, the expression level of MERTK was higher in the proceeding incubation groups than which in the control group except at the 3rd hour. When RPE cells were treated by verapamil, the expression level of MERTK decreased in a dosedependent manner. After RPE cells were pretreated by verapamil , the expression level of MERTK was lower in all the proceeding incubation groups than which in the control group (Plt;0.05). Conclusion MERTK gene and Ca2+ play an important role in sustaining RPE cells phagocytizing ROS. As an up-stream regulator, the receptor tyrosine kinase MERTK keeps RPE cells phagocytizing ROS by starting the intracellular Ca2+.