Effect of Hepes on the fibroblast cerebroside sulfate loading test.

The intact fibroblast cerebroside sulfate loading test is useful because sulfatide hydrolysis can be demonstrated in late onset MLD cell types with 1% or less of normal arylsulfatase A. In such cells, hydrolysis of sulfatide was inhibited when the loading test was carried out in growth media containing the organic ampholyte Hepes. Since Hepes did not affect uptake of sulfatide nor intracellular levels of arylsulfatase A, it was concluded that Hepes inhibited sulfatide hydrolysis by increasing lysosomal pH. The cerebroside sulfate loading test in the presence of Hepes should be useful as a probe for arylsulfatase A dysfunction in atypical MLD fibroblasts.