Histochemical demonstration of acid phosphatase in a human retinal pigment epithelial cell line

The retinal pigment epithelium (RPE) has numerous lysosomes and shows the highest acid phosphatase activity among eye tissues. In an established cell line of human RPE (K-1034), acid phosphatase activity, as a lysosome marker was investigated histochemically to evaluate the maintenance of original RPE characteristics. Even after 100 passages, RPE cells showed remarkable enzyme activity, and had numerous electron-dense bodies which were confirmed to be lysosomes. These results show that this cell line can maintain one of the vital functions of the RPE and provide useful experimental material for functional studies of the human RPE.