Accumulation of Sulfate-containing Acid Mucopolysaccharides in I-cell Fibroblasts

A rapid and sensitive papper electrophoretic assay for 35SO4-containing compounds was developed which allowed measurement of 35S-acid mucopolysaccharides synthesized by skin fibroblasts grown in the presence of inorganic 35S-sulfate. Fibroblasts from a skin explant of a patient with I-cell disease when grown in culture accumulated abnormal amounts of 35S-acid mucopolysaccharides and other, as yet unidentified, 35S-labeled compounds. Approximately 75% of the 35S-compounds accumulated by I-cell fibroblasts were not metabolized and remained in the cells after transfer to nonlabeled medium. I-cell fibroblasts differ from fibroblasts derived from classical mucopolysaccharidoses such as Hurler's and Hunter's syndromes in the amount and types of 35S-labeled acid mucopolysaccharides accumulated. I-cell fibroblasts accumulated chondroitin 4- and 6-sulfates (16 per cent), dermatan sulfate (32 per cent), heparan sulfate (32 per cent), and other unidentified 35S-compounds. The unidentified fraction was not hydrolyzed by microbial chondroitinase or heparinase. Attempts to correct the defect in I-cell fibroblasts by growth in the presence of extracts of normal cells resulted in release of only 10 per cent of the accumulated mucopolysaccharides. Under the same conditions, Hurler and Hunter fibroblasts lost over 90 per cent of accumulated mucopolysaccharides.