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Updated: Oct 21, 2026
Depletion and Reconstitution of Macrophages in Mice
Published on: August 1, 2012
5'-Nucleotidase activity of mouse peritoneal macrophages. I. Synthesis and degradation in resident and inflammatory
Abstract:
Mouse resident peritoneal macrophages display sufficient 5'-nucleotidase activity to hydrolyze 58 nm AMP/min per cell protein. This activity increases approximately 163 nm AMP/min per mg after 72 h in culture. The enzyme is renewed in unstimulated cells with a half-time of 13.9 h. The activity is not reduced by treatment of intact cells with a variety of proteolytic enzymes, including trypsin, pronase, urokinase, and plasmin. Cells obtained from an inflammatory exudate have diminished or absent levels of enzyme activity. Endotoxin-elicited cells display enzyme activitiy of 20.9 nm AMP/min per mg, while thioglycollate-stimulated macrophages have no detectable activity. The reduced level of activity in endotoxin-stimulated cells is due to their elevated rate of enzyme degradation, with a half-time of 6.9 h. Their rate of enzyme synthesis is essentially normal. No evidence for latent enzyme activity could be obtained in thioglycollate-stimulated cells, nor do these cells produce any inhibition of normal cell enzyme activity. Serum deprivation reduces the enzyme activity of resident cells to about 45% of control activity. These conditions do not significantly affect the rate of enzyme synthesis, but again are explainable by an increase in the rate of enzyme degradation. Pinocytic rate is elevated in endotoxin-stimulated cells which show a more rapid rate of enzyme degradation than unstimulated cells do. However, in serum-free conditions, the rate of enzyme degradation is doubled with no change in the pinocytic rate of the cells.
Insights
Mouse macrophages possess 5'-nucleotidase activity, which changes with cell stimulation. Inflammatory conditions, like endotoxin or thioglycollate, alter enzyme levels primarily through increased degradation, not synthesis changes.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Mouse resident peritoneal macrophages exhibit significant 5'-nucleotidase activity.
- This enzyme activity is crucial for macrophage function and homeostasis.
- Understanding factors influencing 5'-nucleotidase activity is key to comprehending macrophage responses.
Purpose of the Study:
- To investigate the regulation of 5'-nucleotidase activity in mouse macrophages under various conditions.
- To determine how inflammatory stimuli and serum availability affect enzyme synthesis and degradation.
- To elucidate the mechanisms behind altered enzyme activity in stimulated macrophages.
Main Methods:
- Assessing 5'-nucleotidase activity in cultured resident peritoneal macrophages.
- Treating cells with proteolytic enzymes to test enzyme stability.
- Analyzing enzyme activity in macrophages elicited by endotoxin and thioglycollate.
- Measuring enzyme synthesis and degradation rates.
- Evaluating the impact of serum deprivation and pinocytic rates.
Main Results:
- Resident macrophages show high 5'-nucleotidase activity, which increases in culture.
- Inflammatory stimuli (endotoxin, thioglycollate) lead to diminished activity, primarily due to increased enzyme degradation.
- Enzyme synthesis rates remain largely unaffected by stimulation.
- Serum deprivation also increases enzyme degradation without significantly altering synthesis.
- Elevated pinocytosis in endotoxin-stimulated cells correlates with faster enzyme degradation.
Conclusions:
- Macrophage 5'-nucleotidase activity is dynamically regulated, with degradation being a key control point, especially under inflammatory conditions.
- Stimuli like endotoxin alter enzyme levels by accelerating degradation rather than suppressing synthesis.
- These findings provide insights into macrophage metabolic adaptation during inflammation and stress.
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