Variability of fibroblast lysosomal acid hydrolases with reference to the detection of enzyme deficiencies

The ranges of variability of eight lysosomal acid hydrolases were examined in 47 cultured human skin fibroblast lines through 5 successive subcultures. No overall trend in activity values was found for any of the enzymes tested between the first and final subcultures. Similarly, no significant differences could be found between the overall ranges of fibroblast enzyme activity between 20 clinically normal children and 27 individuals being investigated for non-specific metabolic diseases. It is concluded that for diagnostic reference purposes, wide ranges of normal enzyme values must be established. Such ranges can be validly drawn from a continuation of both clinical groups irrespective of the passage number (up to 5) of the cells at the time of isolation. It is noted that in certain cell lines derived from Fabry and Gaucher patients the 'residual' activity of the expectedly deficient enzyme could not easily be distinguished from the lowest values observed in normals, whereas, as expected, the activity of cells derived from patients with GM1 and GM2 gangliosidoses was markedly reduced.