A microsystem to assay lysosomal enzyme activities in cultured retinal pigment epithelial cells.

A microsystem to assay the activity of lysosomal enzymes in a small number of cultured RPE cells is described. The activities of acid phosphatase, a-mannosidase, B-glucuronidase and N-acetyl-B-glucosaminidase were estimated in different human RPE cultures of varying passages. Some biochemical characteristics for each of the enzyme assays were studied including the effect of pH, the saturating concentrations of the appropriate substrates and the relationship between the enzyme activity and the number of cells assayed. The method presented is straightforward, avoids complicated tissue fractionation procedures and is able to estimate enzyme activities in as few as 10(4) cells.