[A pH increase in human fibroblast lysosomes during accumulation of non-hydrolysable compounds]

The changes in intralysosomal pH were measured in the stationary phase of normal human embryonic fibroblast growth under sucrose loading over a period of 6 to 120 hours and in cells with a typical lysosomal storage pathology, Fabry's disease, using a vital indicator dye, neutral red. It was shown that long-term hypertrophy of the lysosomal compartment during intracellular accumulation of non-hydrolysable compounds is concomitant with a pH increase, on the average, by 0.4 units. The highest values of pH (7.0-7.2) were seen in large-sized heterogeneic lysosomes of pathological cells. It is suggested that an increase in intralysosomal pH during accumulation of non-hydrolysable compounds leads to deterioration of conditions that are favourable for the acidic hydrolase function.