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Hydrolytic Enzymes in the Neonatal Lung

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Histochemical methods were used to study the development of representative enzymes associated with lysosmal activity in sections of the lung from late fetal, neonatal, and adult rats. Staining for beta-glucuronidase and acid phosphatase was present in the fetus and following birth, and the number and intensity of reactive cells increased to adult levels by 7 to 10 days of life. Reactions for beta-galactosidase were not found in newborn animals, but moderate staining was seen by the 14th day. In contrast to these lysosomal enzymes, high levels of cytochrome oxidase staining were found in all specimens and no age-dependent changes were seen. Acid phosphatase activity was present in nearly all cells in the adult lung, but the indolyl reactions for the glycosidases were localized to single cells. In spite of this resolution, it was not possible to be certain of the identity of many of the reactive cells. The majority appeared to be type II epithelial cells. Alveolar macrophages were usually reactive but relatively few such cells were found, especially in the neonatal specimens. The results of this and other studies indicate that these cells have many common metabolic pathways. Other data, however, suggest a dissimilar origin and function of type II cells and macrophages.

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DOI: 10.21236/AD0857674



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Approved for public release; distribution is unlimited.

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