Osmotically unavailable acid phosphatase activity in normal and growing rat liver.

Evidence is presented on the presence in rat liver homogenates of an aliquot of acid phosphatase activity (lysosomal marker enzyme) which remains latent after extensive hypo-osmotic shock and requires the presence of Triton X-100 to be unmasked. This aliquot is particularly prominent in fraction P, and is markedly increased in new-born rat and regenerating liver.