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Cellular uptake of misonidazole and analogues with acidic or basic functions
Summary
Extracellular pH significantly impacts radiosensitizer uptake in V79-379A cells. Basic radiosensitizers like Ro 03-8799 show increased intracellular concentration at higher pH, crucial for understanding their clinical efficacy.
Area of Science:
- Pharmacology
- Cell Biology
- Radiochemistry
Background:
- Radiosensitizers are crucial for enhancing radiation therapy efficacy.
- Understanding radiosensitizer intracellular concentrations is key to optimizing treatment.
- Extracellular pH is a known factor influencing drug distribution.
Purpose of the Study:
- To measure intracellular concentrations of radiosensitizers in V79-379A cells.
- To investigate the effect of extracellular pH on radiosensitizer uptake.
- To compare experimental results with theoretical pH-gradient calculations.
Main Methods:
- High-performance liquid chromatography (HPLC) was used for quantification.
- Extracellular pH was varied (pHe 6.0-7.85).
- Intracellular pH was estimated using 5,5-dimethyloxazolidine-2,4-dione distribution.
Main Results:
- Misonidazole (2-nitroimidazole) showed constant uptake across pH.
- Ro 03-8799 (weak base) exhibited significant intracellular accumulation at physiological pH.
- Azomycin (weak acid) showed decreased uptake at higher pH.
Conclusions:
- pH-dependent uptake of radiosensitizers, particularly basic compounds, was demonstrated.
- Results align with in vivo distribution and explain in vitro/in vivo efficacy discrepancies.
- Provides insight into clinical use of basic radiosensitizers like Ro 03-8799.