Abstract
Summary: Alveolar macrophages (AMs) obtained from 1-day-old rabbits showed high levels of phospholipid, protein, UNA, and RNA compared to those obtained from 7-day-old, 28-day-old, or adult rabbits. The surfactant material released in alveoli during the perinatal period is extensively phagocytosed by AMs, and appears to be primarily responsible for high phospholipid content of these cells. The high protein, UNA, and KNA levels of AMs may result from phagocytosis of cellular debris.
Of the six lysosomal enzymes of AMs studied, acid phosphatase (AP) and lysozyme activities showed a decline in the first postnatal week. In AP this was followed by no significant change. A steady rise in lysozyme activity after the seventh postnatal day was observed. The activities of cathepsin D and DNase did not show significant changes, whereas β-glucuron-idase and RNase activities of AMs increased significantly within the first postnatal week.
The activities of glucose-6-phosphate dehydrogenase (G-6-PU), 6-phosphogluconate dehydrogenase (6-PGU), lactate dehydrogenase (LDH), and malate dehydrogenase (MDH) in AMs appeared high in AMs of 1-day-old animals compared to other time periods studied. Following a significant decline in these activities in the first postnatal week, a peak was observed in the activities of G-6-PD, 6-PGD, and LDH at 28 days.
Speculation: A high concentration of phospholipid in AMs obtained from newborn animals suggests that AMs play an important role in the removal of excess surfactant from the newborn lung. A relative increase in hexosemonophosphate shunt activities over glycolytic or Krebs cycle activities after birth and an increase in lysozyme activity after the first postnatal week may contribute to the capacity of AMs to kill and degrade the microorganisms.
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Nerurkar, L., Zeligs, B. & Bellanti, J. Maturation of the Rabbit Alveolar Macrophage during Animal Development. II. Biochemical and Enzymatic Studies. Pediatr Res 11, 1202–1207 (1977). https://doi.org/10.1203/00006450-197712000-00007
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DOI: https://doi.org/10.1203/00006450-197712000-00007