Abstract |
In order to develop new imaging markers for brain hypoxia, two lipophilic nitroimidazoles, 1-(3-fluoropropyl)-2-nitroimidazole (FPN) and 1-(8-fluorooctyl)-2-nitroimidazole (FON) were synthesized and labeled with fluorine-18. The octanol/water partition coefficients were measured as an indication of lipophilicity, giving values of logP=0.28 for FPN and logP=2.72 for FON, respectively, which are in the range thought to be optimal for the diffusion of molecules across the blood-brain barrier. It was suggested from a comparative study of in vitro radiosensitization in V79 cells that these lipophilic analogs may have reduction potentials close to those of fluoromisonidazole ( FMISO) and misonidazole (MISO), known hypoxic cell radiosensitizers. The preparation of 18F-labeled FON (18FON) and FPN (18FPN) was achieved via two-steps through [18F] fluoride ion displacement of tosylate precursors, in reasonable radiochemical yields. Tissue distribution of 18FPN and 18FON in normal rats and tumor-bearing mice after intravenous injection was investigated and compared to the behavior of 18F-labeled FMISO (18FMISO), a proven hypoxic imaging agent. The high lipophilicity of 18FON and 18FPN resulted in increased initial uptake into normal rat brain, relative to 18FMISO, followed by a rapid washout from brain. Both of these lipophilic analogs had significantly lower tumor uptake and lower tumor-to-blood ratios than 18FMISO, suggestive of a poor trapping mechanism within the tumor tissue. Neither 18FON or 18FPN offers improved biological properties over 18FMISO as a potential agent for use in brain hypoxic imaging.
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Authors | F Yamamoto, H Oka, S Antoku, Y Ichiya, K Masuda, M Maeda |
Journal | Biological & pharmaceutical bulletin
(Biol Pharm Bull)
Vol. 22
Issue 6
Pg. 590-7
(Jun 1999)
ISSN: 0918-6158 [Print] Japan |
PMID | 10408232
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
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Chemical References |
- 1-(3-fluoropropyl)-2-nitroimidazole
- 1-(8-fluorooctyl)-2-nitroimidazole
- Fluorine Radioisotopes
- Imidazoles
- Nitro Compounds
- Nitroimidazoles
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Topics |
- Animals
- Brain
(metabolism)
- Female
- Fluorine Radioisotopes
- Hypoxia
(diagnostic imaging)
- Imidazoles
(chemical synthesis, chemistry, pharmacokinetics)
- Male
- Mice
- Mice, Inbred C3H
- Neoplasms, Experimental
(metabolism)
- Nitro Compounds
(chemical synthesis, chemistry, pharmacokinetics)
- Nitroimidazoles
(chemical synthesis, pharmacokinetics)
- Radionuclide Imaging
- Rats
- Rats, Wistar
- Solubility
- Tissue Distribution
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