Detection of acid-beta-galactosidase activity in viable human fibroblasts by flow cytometry

The fluorogenic substrate fluorescein-di-beta-D-galactopyranoside was used to detect acid beta-galactosidase in intact cultured human fibroblasts. The accumulation of intracellular fluorescein, as measured by flow cytophotometry was linear with the incubation time in three control strains. The two fibroblast strains from patients with acid beta-galactosidase deficiency did not show an accumulation of intracellular fluorescence. Within one control cell population there was a positive correlation between the amount of accumulated intracellular fluorescein fluorescence and the specific acid beta-galactosidase activity as measured biochemically on sorted cells from different zones of the fluorescence distribution. No correlation was found between the specific acid beta-galactosidase activity and the fluorescein fluorescence of three different control cell strains.