Yoko Kanazawa

Metabolic pathway of 2-deoxy-2-fluoro-D-glucose studied by F-19 NMR

The behavior of 2-deoxy-2-fluoro-D-glucose (FDG) in mouse has been studied by F-19 NMR method for long period. The F-19 NMR signals of FDG or its metabolites were observed in tissues without serious broadening. FDG was found to be accumulated in organs in the form of FDG or FDG-6-phosphate and 2-deoxy-2-fluoro-D-mannose (FDM) or FDM-6-phosphate, and the latter dominated the former in the heart sampled at 24 hr or later. The fluorine compounds were excreted in urine in both forms. The clearance was rapid from brain, liver, and blood, but was slow from heart.

19F NMR of 2-deoxy-2-fluoro-D-glucose for tumor diagnosis in mice. An NDP-bound hexose analog as a new NMR target for imaging

A well‐known radiopharmaceutical 2‐deoxy‐2‐fluoro‐D‐glucose widely used for positron emission tomography diagnosis in terms of glucose utilization, was re‐evaluated here as a nuclear magnetic resonance pharmaceutical for cancer detection. The uptake and metabolism of FDG in the experimental tumor, MH134, transplanted to the peritoneum of C3H mice as an ascitic tumor was studied extensively by ex vivo 19F NMR. Prolonged retention of FDG and its metabolites over 2 days was confirmed in the tumor cells as well as in the heart. In these tissues, the 6‐phosphate of the injected compound was converted reversibly to its epimer 2‐deoxy‐2‐fluoro‐D‐mannose and further to their NDP bound forms. The metabolites were almost cleared within a day from the other healthy organs where the formation of NDP‐2‐deoxy‐2‐fluoro‐D‐mannose was low. Thus, the 19F NMR signal of NDP–FDM detected 1 day after the FDG injection could be used as a target signal for tumor detection. Through the use of in vivo 19F NMR spectra and 19F chemical shift images, the feasibility of this proposal was demonstrated. It was concluded that FDG–NMR has a potential for tumor diagnosis in animals.

Radiosynthesis, rodent biodistribution, and metabolism of 1-deoxy-1-[18F]fluoro-d-fructose

Fluorine-18 labeled analog of D-fructose, 1-deoxy-1-[18F]fluoro-D- fructose (1-[18F]FDFrc), was synthesized by nucleophilic substitution of [18F]fluoride ion and the effect of the fluorine substitution on its in vivo metabolism was investigated. The tissue distributions of 1-[18F]FDFrc in rats and tumor bearing mice showed initial high uptake and subsequent rapid washout of the radioactivity in the principal sites of D-fructose metabolism (kidneys, liver and small intestine). The uptakes in the brain and tumor (fibrosarcoma) were the lowest and moderate, respectively, but tended to increase with time. The in vivo metabolic studies of 1-[18F]FDFrc and nonradioactive 1-FDFrc in mouse brain and tumor showed that the fluorinated analog remained unmetabolized in these tissues, indicating that the substitution of fluorine at the C-1 position produces a nonmetabolizable analog of D-fructose. Thus, 1-[18F]FDFrc had no features of a metabolic trapping tracer without showing any appreciable organ or tumor specific localization.

The lateral diffusion coefficient of lecithin molecules in single bilayer vesicles studied by 14N NMR

Abstract The 14 N nuclear relaxation times T 1 and T 2 in egg yolk phosphatidylcholine have been observed in single bilayer vesicles dispersed in the media of different viscosities, 1 H 2 O and 2 H 2 O. The lateral diffusion coefficient of lipid molecule D has been calculated according to the method reported earlier: D = 2.2 × 10 −8 cm 2 s −1 in 1 H 2 O and 2.1 × 10 −8 cm 2 s −1 in 2 H 2 O at 20°C. They are in excellent agreement. This result gives a strong basis of usefulness of 14 N NMR method in the evaluation of D without introducing any system perturbation.

Reorientational motion of acetone in solutions

Abstract Dipolar correlation functions of acetone in various solvents are obtained by Fourier transform of infrared spectra. The analysis of the shapes of correlation functions shows that the reorientational process is diffusional in the time scale longer than about 0.3 × 10 −12 sec. In nonpolar solvents the ratios of correlation times τ A : τ B : τ C do not vary in different solvents, and the reorientation around b axis is more restricted than around the other axis. The length of correlation time is dependent on the density of solvent rather than the viscosity. These observations are unexpected if only the electrostatic interaction is considered. In polar solvents correlation times are longer than in nonpolar solvents and the tendency is especially remarkable in τ B . An electrostatic interaction between polar molecules seems to be responsible for these observations. The solvent effect on the frequency shifts of carbonyl stretching vibration is consistent with the result of correlation times.

Inhibition of Chloride Binding to the Anion Transport Site by Diethylpyrocarbonate Modification of Band 3

SummaryThe line widths of35Cl− nuclear magnetic resonances were used to measure chloride binding by Band 3. Since this procedure related directly to binding, the data obtained may be interpreted more unequivocally than affinities derived from kinetic data which could be related to either translocation or binding. Chloride binding to the active sites in Band 3 was assessed from that portion of the total line width which was sensitive to 4,4′-dinitrostilbene-2,2′-disulfonic acid. These sites appeared to be completely inhibited by treatment of erythrocyte membranes with diethylpyrocarbonate. This result is consistent with our previous observation that this reagent inhibits anion transport in resealed erythrocyte ghosts (Izuhara, Okubo & Hamasaki, 1989,Biochemistry28:4725–4728). Hydroxylamine could not reverse the diethylpyrocarbonate inhibition of chloride binding to Band 3. The pH-dependence of diethylpyrocarbonate reactivity suggests that the modified residues may be those of histidine.

Quantitative 19F imaging of nmol-level F-nucleotides/-sides from 5-FU with T2 mapping in mice at 9.4T

A unique acquisition method is proposed for quantitative, high‐sensitivity 19F MR spectroscopic imaging for the study of drug distribution aiming at nmol‐level metabolite information in mice. The use of fast spin echo (FSE) at 9.4T allowed us to obtain whole‐body images with minimal effect of magnetic susceptibility and to acquire several metabolite signals simultaneously by the method of interleaved multifrequency selection. Modified 2‐shot FSE was designed for simultaneous, high‐sensitivity 19F imaging and T2 mapping. A time course study including all the main metabolites at 10‐minute resolution was attained with an oral dose of 1–2 mmol 5‐fluorouracil (5‐FU) (130–260 mg)/kg in mice. With acquisition parameters optimized for in vivo T2 of 40 ms, images of F‐nucleotides/‐sides, effective anabolites of the anticancer drug 5‐FU, were obtained at the level of 200 nmol in the tumor for all the mice studied with a linear correlation (R = 0.96) between image intensity and the quantity determined in the excised tissue. The method exhibits potential capability of molecular imaging with a variety of 19F‐labeled compounds and drug evaluation. Magn Reson Med, 2009.

Application of 19F chemical shift imaging in studies of mice with orally administered 5-fluorouracil

In vivo quantitative metabolic mapping is an ideal tool for pharmacokinetic studies. Oral 5‐fluorouracil (5‐FU) and its metabolites in mice were imaged simultaneously by the 19F fast spin echo (FSE) sequence using interleaved frequency selection at 9.4T. However, 5‐FU images in the small intestine have never been obtained regardless of concentration. The reason for the discrepancy between image intensity and concentration was T2. At a pH above 6, a dramatic decrease in T2 of a 19F 5‐FU signal in an aqueous solution was found; T2 was shorter in the small intestine (14 ms) than in the stomach (52 ms). The 19F CSI sequence in FID sampling mode was employed for detecting short T2 signals. With a 13‐min resolution time, the detection of the 5‐FU signals in the region of the small intestine (0.6 mmol/kg) was successful with a 5 × 5 mm2 in‐plane resolution. Furthermore, two signals separated by 2 ppm were clearly distinguishable, but failed to be separately detectable with the 19F FSE sequence. For quantitative simultaneous monitoring of 5‐FU and its metabolites of varying T2, the 19F CSI sequence in FID sampling mode was found to be superior to the 19F FSE sequence. Magn Reson Med 46:864–869, 2001.

Use of a commercial waveform analyzer in a pulse FT NMR system

Abstract An NMR system composed of a home-made pulse system and a commercial wave form analyzer is tested for 14N resonances. The 14N signals of various widths ranging from less than 1 Hz to 500 Hz of various intensities can be obtained successfully by this system. An inexpensive system of this kind is found to be very useful for nuclear species which do not require fine resolution.

A study of head groups in phosphatidylcholine-cholesterol bilayers by 14N-NMR

Abstract The 14N nuclear relaxation times of egg phosphatidylglycerol (EPC) in mixed EPC-cholesterol small unilamellar vesicles were measured for the first time. No dependence of longitudinal relaxation time T 1 ( 14 N) on cholesterol content was observed up to a molar ratio of cholesterol to total lipid Xch = 0.4. The 14N nuclear quadruple coupling constant e2qQ/h and the rapid segmental motions at the positively charged group of EPC are not affected by the moderate increase in the area available to each head group by the cholesterol incorporation. The increase in the 14N line width with cholesterol was analyzed using 14N residual quadrupole splittings Δν Q ( 14 N) . The line width of the high resolution spectrum of single bilayer vesicles has a considerable contribution from the lateral diffusion of EPC molecules. The diffusion coefficient D decreases abruptly to one half between Xch = 0.1 and 0.2 at 20°C. This result is in good agreement with that obtained for a multilamellar phase by Rubenstein et al. (Proc. Natl. Acad. Sci. U.S.A., 76 (1979) 15–18), showing an essential similarity between unilamellar and multilamellar phases.