(D, E) Rat liver lysosomes incubated or not with 1 mM CaCl2 (+Ca2+) were subjected to Triton X‐114 extraction and sucrose density gradients centrifugation. Levels of cathepsin A (D) and carboxypeptidase A activity (E) were measured in each fraction by immunoblot or using a standardized colorimetric assay, respectively. Values in (E) are expressed as times the activity in untreated membranes and are mean+s.e. of two experiments. 