Lysosomal Acid Hydrolase Activities in the Lungs of Fetal, Neonatal, Adult, and Senile Mice

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Abstract
The activities of four lysosomal acid hydrolases (LAH) in the lungs of two strains of mice changed significantly throughout the life cycle. In the C57B1/6J animals, acid phosphatase (AP) and β- glucuronidase (β-G) were maximally active during early neonatal life then gradually declined to the adult levels by 4–5 weeks of age. After reaching the adult level, acid phosphatase activities did not change significantly through 20 months of age. In contrast, β-G activities increased markedly with advanced age. N-Acetyl-β-D-glucosaminidase (GAD) activities did not change significantly during late fetal, neonatal or young adult stages but increased significantly with advancing age. In the lungs of the CFW animals, the increase in activities of β-G and GAD between young adult life and advanced age was highly significant, whereas there was no notable change in the activities of acid phosphatase or arylsul-fatase (AS). The specific activities of the hydrolases in the lungs of the C57B1/6J strain were quite similar to those in the lungs of the CFW strain. The activities of all four hydrolases were markedly elevated in two spontaneous adenomatous tumors found in the lungs of old mice. The data indicate that LAH play a significant role in lung growth and maturation, and in changes associated with aging.