[C-14] METHYLAMINE ACCUMULATION IN CULTURED HUMAN SKIN FIBROBLASTS - A BIOCHEMICAL TEST FOR LYSOSOMAL STORAGE AND LYSOSOMAL DISEASES

Incorporation of the lysosomotropic amine [C-14]methylamine by fibrobl asts cultured from patients with lysosomal storage diseases and from c ontrols was used to estimate the size of the lysosomal compartment. Al l cell lines from patients with infantile and juvenile forms of mucopo lysaccharidoses, mucolipidoses and oligosacharidoses showed markedly i ncreased radioactivity compared with the normal range of controls. In cells from patients with sphingolipidoses and adult forms of storage d iseases, however, methylamine accumulation was not significantly incre ased. Experimentally induced lysosomal storage by enzyme inhibitors (l eupeptin, suramin) also caused increased methylamine accumulation. Whe n the lysosomal pH was determined with fluorescein isothiocyanate-dext ran, it was in the range of normal controls (pH 4.7-5.0) in patients c ells. Thus, [C-14]methylamine accumulation should depend on the volume rather than differences in acidity of the lysosomal compartment and b e a measure of its eventual pathological enlargement. We conclude that the determination of [C-14]methylamine accumulation in fibroblasts pr ovides a valuable tool in the screening for a variety of lysosomal sto rage disorders.