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Autoradiographic evidence for the impermeability of mouse peritoneal macrophages to tritiated streptomycin
Abstract:
Cultured mouse peritoneal macrophages were found to be relatively impermeable to streptomycin. Based on radioactivity measurements and radioautographic evidence, macrophages were impermeable to tritiated dihydrostreptomycin for periods up to 20 hr of incubation. Little or no intracellular streptomycin could be detected even when incubation was carried out in the presence of therapeutic blood levels of carrier dihydrostreptomycin. When the cultured mouse macrophages were allowed to phagocytize staphylococci, yeast cells, or polystyrene latex particles in the presence of tritiated streptomycin, the impermeability of the cells to the antibiotic was not affected. These observations suggested that the process of phagocytosis does not facilitate the intracellular accumulation of streptomycin, as seems to be the case for the fixed phagocytic cells of the liver.
Insights
Mouse macrophages are impermeable to streptomycin, even during phagocytosis. This study shows that streptomycin does not easily enter these immune cells, impacting its effectiveness against intracellular pathogens.
Area of Science:
- Microbiology
- Immunology
- Pharmacology
Background:
- Streptomycin is a crucial antibiotic for treating bacterial infections.
- Understanding antibiotic penetration into immune cells like macrophages is vital for optimizing treatment strategies.
- Macrophages play a key role in pathogen clearance, making their intracellular environment critical for antibiotic efficacy.
Purpose of the Study:
- To investigate the permeability of cultured mouse peritoneal macrophages to streptomycin.
- To determine if phagocytosis enhances streptomycin uptake by macrophages.
- To compare streptomycin uptake in macrophages with that in fixed phagocytic cells.
Main Methods:
- Cultured mouse peritoneal macrophages were incubated with tritiated dihydrostreptomycin.
- Radioactivity measurements and radioautography were used to quantify intracellular streptomycin.
- Macrophages were induced to phagocytize bacteria, yeast, and latex particles in the presence of streptomycin.
Main Results:
- Macrophages demonstrated significant impermeability to streptomycin for up to 20 hours.
- Therapeutic blood levels of streptomycin did not lead to detectable intracellular accumulation.
- Phagocytosis of various particles did not alter the impermeability of macrophages to streptomycin.
Conclusions:
- Cultured mouse peritoneal macrophages are largely impermeable to streptomycin.
- Phagocytosis does not facilitate the intracellular entry or accumulation of streptomycin in these cells.
- This impermeability may limit the efficacy of streptomycin against intracellular pathogens within macrophages.