Abstract
A subcellular fraction prepared from a heteroploid human cell line had the characteristics of lysosomes in that it contained sedimentable acid hydrolases which could be solubilized by adding Triton X-100. Appearance of soluble acid phosphatase activity during acid incubation of these lysosomes was characterized by an initial rapid rise with no further increase until the third hour of incubation. In addition, sedimentable activity increased, suggesting an alteration of permeability of lysosomes to substrate. Ultraviolet irradiation accelerated the release of acid phosphatase during a 90 min period but was not characterized by the initial rapid rise of soluble activity observed with acid incubation. The effects of acid incubation and ultraviolet irradiation were temperature dependent, with no significant release of enzyme activity at 4 °C. Lysosomes from cells grown with 1.5 × 10 −4 M prednisolone released less acid phosphatase during acid incubation. Those from cells grown in concentrations of steroids as low as 2 × 10 −6 M were similarly affected, but only during the first two hours of acid incubation. Cells grown with 4 × 10 −4 M prednisolone showed inhibition of net protein synthesis and no enhancement of lysosome stability.
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