The development of lysosomal apparatus. I. Lysosomal enzyme activities in the liver of mice at perinatal stages and those of their mothers.

The enzymatic activity of five acid hydrolases: acid phosphatase, arylsulfatase A, deoxyribonuclease, beta-glucuronidase, and cathepsin D, was assayed in fetal (fifteenth and eighteenth days of pregnancy) and neonatal (Days 0, 5, 10, and 15 post-partum) mouse liver. With the exception of cathepsin D, the activity increased around birth to levels varying according to the enzyme. Histochemical observations of other authors appear to justify, at least in part, the present results, which indicate that late days of fetal development and early neonatal life may constitute a transitional stage to full lysosomal enzyme functionality of the adult organ. The livers of the mothers were also assayed for the same enzymes. Each activity showed a peculiar pattern which was, in turn, different from that found in the liver of the litter for the same enzyme, probably as a cause of the metabolic requirement of the gland. The hypothesis that the lysosomes are heterogeneous in their enzyme composition is suggested by the variety of enzymatic patterns found in the liver of the litters and their mothers.