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Arginase production by peritoneal macrophages: a new assay
Abstract:
The arginase activity of murine mononuclear cells was assessed with a new highly sensitive radioassay. Adherent mononuclear cells obtained by peritoneal lavage from normal mice contain significant quantities of enzyme. This was released in culture and continued synthesis could be blocked with cycloheximide. Arginase activity was not found in adherent or non-adherent mononuclear cells from the spleen. Peritoneal cells obtained from mice infected with P. berghei or from mice injected with LPS intraperitoneally had higher arginase activity than cells from control mice.
Insights
Murine mononuclear cells, particularly those from the peritoneum, exhibit significant arginase activity. This enzyme
Area of Science:
- Immunology and Biochemistry
- Cell Biology
Background:
- Arginase is an enzyme involved in the urea cycle and amino acid metabolism.
- Its role in immune cells, particularly mononuclear cells, is not fully understood.
- Previous studies have suggested arginase activity in various immune cells, but sensitive assays are needed for precise quantification.
Purpose of the Study:
- To develop and utilize a highly sensitive radioassay for quantifying arginase activity in murine mononuclear cells.
- To investigate the presence and characteristics of arginase in different mononuclear cell populations (peritoneal vs. splenic).
- To examine the modulation of arginase activity in peritoneal cells under inflammatory conditions.
Main Methods:
- Isolation of mononuclear cells from murine peritoneal lavage and spleen.
- Culturing of peritoneal cells to assess enzyme release and synthesis.
- Application of a novel, highly sensitive radioassay to measure arginase activity.
- Inhibition of protein synthesis using cycloheximide to study enzyme synthesis.
- Induction of inflammation using Plasmodium berghei infection and lipopolysaccharide (LPS) injection.
Main Results:
- Significant arginase activity was detected in adherent mononuclear cells from normal mouse peritoneum.
- This enzyme activity was released into culture and its synthesis was inhibited by cycloheximide, indicating active production.
- No significant arginase activity was found in either adherent or non-adherent mononuclear cells from the spleen.
- Peritoneal cells from mice infected with P. berghei or treated with LPS showed significantly elevated arginase activity compared to controls.
Conclusions:
- Adherent peritoneal mononuclear cells are a major source of arginase activity in mice.
- Arginase synthesis in these cells is an active, regulated process.
- Inflammatory stimuli, such as P. berghei infection and LPS, markedly increase arginase activity in peritoneal cells, suggesting a role in the immune response.