Analysis of the Radiorespirometric pattern after administration of [U-14C] glucose to Ehrlich ascites tumor-bearing mice

Ehrlich ascites tumor-bearing mice were subjected to 14CO2 radiorespirometric analysis after administration of [U-14C]glucose, and the results were compared with the levels of host liver glycolytic enzyme activities and the uptake of the radioactivity into the liver. After IP administration of [U-14C]glucose, there was a progressive decline in respiratory 14CO2 after the transplantation of the Ehrlich ascites tumor cells. The peak time (PT) was about 10 min on day 1, but thereafter was increasingly delayed, and could not be determined on day 13. Peak height (PH) and yield value (YV) were both considerably decreased, and again the magnitudes of the changes increased with the time after transplantation of the tumor cells. Glycolytic enzyme activities in the host liver were at normal levels 13 days after transplantation of the tumor cells. The uptake of the radioactivity into the liver after IP administration of [U-14C]glucose began to decline from day 5 and was 50% the value in normal mice 13 days after transplantation of the tumor cells. THese results indicate that the radiorespirometric patterns with [U-14C]glucose reflects hepatic biochemical changes rather well.     

Biodistribution of intravenously injected [14C] doxorubicin and [14C] daunorubicin in mice: concise communication

[14C] doxorubicin (adriamycin) and [14C] daunorubicin (daunomycin) are cardiotoxic antibodies used in cancer therapy. These drugs were examined as possible agents for the measurement of regional myocardial blood flow. The antibiotics were injected intravenously into mice, which were then killed after various intervals. At a chemical dosage of 0.5 mg per kilogram, the content of the heart never exceeded 0.60% of the administered dose for doxorubicin and 0.55% for daunorubicin. The cardiotoxic effect of these drugs, therefore, is probably related to a specific sensitivity of the heart, rather than to an avid uptake of the drugs by the cardiac muscle. Further studies seem warranted, using a lower chemical dosage and higher specific activity.     

Radiochromatographic resolution of [14C]DL-tryptophan, [14C]DL-phenylalanine and [35S]DL-methionine on a cellulose column

[¹⁴C]DL-Tryptophan, [¹⁴C]DL-phenylalanine and [³⁵S]DL-methionine were resolved using cellulose column chromatography. The assignment for the resolved enantiomers was carried out by means of co-chromatography with non-labeled DL-amino acids after modification with fluorodinitrobenzene. The optical purity of the enantiomers was estimated to be greater than 99%. The resolved enantiomers were provided for bioassay, showing that the enantiomer was biochemically active.     

[11C]Sorafenib: Radiosynthesis and preclinical evaluation in tumor-bearing mice of a new TKI-PET tracer

IntroductionTyrosine kinase inhibitors (TKIs) like sorafenib are important anticancer therapeutics with thus far limited treatment response rates in cancer patients. Positron emission tomography (PET) could provide the means for selection of patients who might benefit from TKI treatment, if suitable PET tracers would be available. The aim of this study was to radiolabel sorafenib (1) with carbon-11 and to evaluate its potential as TKI-PET tracer in vivo.MethodsSynthetic methods were developed in which sorafenib was labeled at two different positions, followed by a metabolite analysis in rats and a PET imaging study in tumor-bearing mice.Results[methyl-¹¹C]-1 and [urea-¹¹C]-1 were synthesized in yields of 59% and 53%, respectively, with a purity of > 99%. The identity of the products was confirmed by coinjection on HPLC with reference sorafenib. In an in vivo metabolite analysis [¹¹C]sorafenib proved to be stable. The percentage of intact product in blood–plasma after 45 min was 90% for [methyl-¹¹C]-1 and 96% for [urea-¹¹C]-1, respectively. Due to the more reliable synthesis, further research regarding PET imaging was performed with [methyl-¹¹C]-1 in nude mice bearing FaDu (head and neck cancer), MDA-MB-231 (breast cancer) or RXF393 (renal cancer) xenografts. Highest tracer accumulation at a level of 2.52 ± 0.33 %ID/g was observed in RXF393, a xenograft line extensively expressing the sorafenib target antigen Raf-1 as assessed by immunohistochemistry.ConclusionIn conclusion, we have synthesized [¹¹C]sorafenib as PET tracer, which is stable in vivo and has the capability to be used as PET tracer for imaging in tumor-bearing mice.     

Hepatic UDP-glucose 13C isotopomers from [U-13C]glucose: a simple analysis by 13C NMR of urinary menthol glucuronide.

Menthol glucuronide was isolated from the urine of a healthy 70-kg female subject following ingestion of 400 mg of peppermint oil and 6 g of 99% [U-(13)C]glucose. Glucuronide (13)C-excess enrichment levels were 4-6% and thus provided high signal-to-noise ratios (SNRs) for confident assignment of (13)C-(13)C spin-coupled multiplet components within each (13)C resonance by (13)C NMR. The [U-(13)C]glucuronide isotopomer derived via direct pathway conversion of [U-(13)C]glucose to [U-(13)C]UDP-glucose was resolved from [1,2,3-(13)C(3)]- and [1,2-(13)C(2)]glucuronide isotopomers derived via Cori cycle or indirect pathway metabolism of [U-(13)C]glucose. In a second study, a group of four overnight-fasted patients (63 +/- 10 kg) with severe heart failure were given peppermint oil and infused with [U-(13)C]glucose for 4 hr (14 mg/kg prime, 0.12 mg/kg/min constant infusion) resulting in a steady-state plasma [U-(13)C]glucose enrichment of 4.6% +/- 0.6%. Menthol glucuronide was harvested and glucuronide (13)C-isotopomers were analyzed by (13)C NMR. [U-(13)C]glucuronide enrichment was 0.6% +/- 0.1%, and the sum of [1,2,3-(13)C(3)] and [1,2-(13)C(2)]glucuronide enrichments was 0.9% +/- 0.2%. From these data, flux of plasma glucose to hepatic UDPG was estimated to be 15% +/- 4% that of endogenous glucose production (EGP), and the Cori cycle accounted for at least 32% +/- 10% of GP.     

Biodistribution of [14C]PnAO in rats

The biodistribution of [14C]3,3'-(1,3-propanediyldiimino)-bis(3-methy 1-2-butanone)-dioxime, [( 14C]PnAO) was determined in anesthetized rats. The results of this study show that there is no significant brain accumulation or retention of the uncomplexed ligand in the brain.     

Localized proton NMR observation of [3-13C]lactate in stroke after [1-13C]glucose infusion.

To assess whether elevated lactate in stable stroke is being actively produced from blood glucose localized 1H NMR stimulated echo spectra were obtained from a patient in the region of a 32-day-old cortical infarct before and 60-100 min after infusion of [1-13C]glucose. Prior to the infusion the spectrum from the region of the infarct contained an elevated resonance from C3 lactate and a greatly reduced resonance from N-acetyl groups relative to an unaffected contralateral region. After the infusion two additional resonances were observed at 62 and -64 Hz relative to the unlabeled resonance of C3 lactate which were assigned on the basis of chemical shift and relative intensity to [3-13C]lactate. The [3-13C]lactate fractional enrichment in the infarct region was measured to be 32% which is within error one-half the average [1-13C]plasma glucose enrichment during the postinfusion NMR measurement. The result suggests that the stroke lactate pool was completely derived from infused glucose.     

Detection of metabolites in rabbit brain by 13C NMR spectroscopy following administration of [1-13C]glucose

1H-decoupled 13C NMR spectra (20.2 MHz) of the living rabbit brain were collected with a surface coil following the intravenous infusion of [1-13C]glucose. Within 15 min of infusion, the alpha and beta anomers of glucose were detected and, shortly thereafter, the carbon atoms at positions C4, C3, and C2 of glutamate and(or) glutamine. After reductions of inspired oxygen from 30 to 5%, lactate C3 was detected. The intensity of the lactate resonance rose progressively during hypoxia and later fell during recovery with oxygen. The 13C fractional isotopic enrichment of arterial blood glucose was measured by 1H NMR providing information on the rate and extent of blood glucose labeling.     

Distribution and stability of [111In]bleomycin and its fractions in tumor-bearing mice

The tissue distributions in glioma-bearing mice given injections of [¹¹¹In]bleomycin (BLM) indicated that tumor concentrations and ratios of tumor to blood, muscle and brain for [¹¹¹In]BLM-B₂ and -A₂ were higher than those for unfractionated [¹¹¹In]BLM. Autoradiographs of electrophoretic gels of urine containing [¹¹¹In]BLM or one of its fractions differed from those containing ¹¹¹InCl₃ [¹¹¹In]BLM and its fractions (A₂ and B₂) were found to be stable in vivo. The fractions may be more useful in the clinic than [¹¹¹In]BLM.     

Effect of irradiation and chemotherapeutic agents on the capillaries of Ehrlich ascites carcinoma of mice.

The effect of irradiation and chemotherapeutic agents on the capillaries of experimental solid tumours was analysed by the resin cast method. The most evident change of the 5 vascular layers was rarefaction of the newly produced extruding capillaries on the surface of the tumour mass, which was related to the tumour growth.     

[C]Formaldehyde revisited: considerable concurrent [C]formic acid formation in the low-temperature conversion of [C]carbon dioxide into [C]formaldehyde

The reduction of [¹¹C]carbon dioxide with lithium aluminium hydride in diethyl ether at temperatures ranging from −56°C to 19°C was studied. In contrast to what others have reported, considerable amounts of [¹¹C]formic acid were found at all studied temperatures.     

Comparison of [3,4‐13C2]glucose to [6,6‐2H2]glucose as a tracer for glucose turnover by nuclear magnetic resonance

A recently introduced tracer, [3,4‐¹³C₂]glucose, was compared to the widely used tracer, [6,6‐²H₂]glucose, for measurement of whole‐body glucose turnover. The rate of glucose production (GP) was measured in rats after primed infusions of [3,4‐¹³C₂]glucose, [6,6‐²H₂]glucose, or both tracers simultaneously followed by a constant infusion of tracer(s) over 90 min. Blood glucose was purified and converted into monoacetone glucose for analysis by ¹³C NMR (for [3,4‐¹³C₂]glucose) or ¹H and ²H NMR (for [6,6‐²H₂]glucose). The values of GP measured during infusion of each single tracer were not significantly different. In rats infused with both tracers simultaneously, GP was identical as reported by each tracer, 42 ± 4 μmol/kg/min. Since ²H and ¹³C enrichment in glucose is typically much less than 2% for in vivo studies, [3,4‐¹³C₂]glucose does not interfere with measurements of ¹³C or ²H enrichment patterns and therefore is valuable when multiple metabolic pathways are being evaluated simultaneously. Magn Reson Med 53:1479–1483, 2005. © 2005 Wiley‐Liss, Inc.     

Evaluation of Radiation Dose Resulting from the Ingestion of [3H]- and [14C]thymidine in the Rat

Summary

Average doses to rat tissues from the ingestion of 2-[¹⁴C]thymidine were compared with those from methyl-[³H]thymidine or 6-[³H]thymidine. Among the three precursors, [¹⁴C]thymidine gave the highest dose to spleen and small intestine. The doses to other tissues from [¹⁴C]thymidine were almost the same or lower as compared with those from [³H]thymidine, irrespective of the 9 times higher β-ray energy of ¹⁴C than that of ³H. In the case of [¹⁴C]thymidine, most of the dose was given by radioactivity incorporated into the organic tissue constituents (non-volatile radioactivity). In the case of [³H]thymidine, however, the dose contributions by non-volatile radioactivity were very small and the major contributions were rather from volatile radioactivity (³HHO), formed by degradation of [³H]thymidine. No significant difference in their total doses was found between the two [³H]precursors, but the dose from non-volatile radioactivity alone was 2–3 times higher with methyl-[³H]thymidine than with 6-[³H]thymidine. Estimates of the dose to cell nuclei in various tissues after the ingestion of [³H]thymidine were also made in order to predict more precisely possible radiation hazards.     

Equivalence of arterial and venous blood for [11C]CO2-metabolite analysis following intravenous administration of 1-[11C]acetate and 1-[11C]palmitate

PurposeSampling of arterial blood for metabolite correction is often required to define a true radiotracer input function in quantitative modeling of PET data. However, arterial puncture for blood sampling is often undesirable. To establish whether venous blood could substitute for arterial blood in metabolite analysis for quantitative PET studies with 1-[¹¹C]acetate and 1-[¹¹C]palmitate, we compared the results of [¹¹C]CO₂-metabolite analyses performed on simultaneously collected arterial and venous blood samples.MethodsPaired arterial and venous blood samples were drawn from anesthetized pigs at 1, 3, 6, 8, 10, 15, 20, 25 and 30 min after i.v. administration of 1-[¹¹C]acetate and 1-[¹¹C]palmitate. Blood radioactivity present as [¹¹C]CO₂ was determined employing a validated 10-min gas-purge method. Briefly, total blood ¹¹C radioactivity was counted in base-treated [¹¹C]-blood samples, and non-[¹¹C]CO₂ radioactivity was counted after the [¹¹C]-blood was acidified using 6 N HCl and bubbled with air for 10 min to quantitatively remove [¹¹C]CO₂.ResultsAn excellent correlation was found between concurrent arterial and venous [¹¹C]CO₂ levels. For the [¹¹C]acetate study, the regression equation derived to estimate the venous [¹¹C]CO₂ from the arterial values was: y = 0.994x + 0.004 (r² = 0.97), and for the [¹¹C]palmitate: y = 0.964x ? 0.001 (r² = 0.9). Over the 1–30 min period, the fraction of total blood ¹¹C present as [¹¹C]CO₂ rose from 4% to 64% for acetate, and 0% to 24% for palmitate. The rate of [¹¹C]CO₂ appearance in venous blood appears similar for the pig model and humans following i.v. [¹¹C]-acetate administration.ConclusionVenous blood [¹¹C]CO₂ values appear suitable as substitutes for arterial blood samples in [¹¹C]CO₂ metabolite analysis after administration of [¹¹C]acetate or [¹¹C]palmitateAdvances in Knowledge and Implications for Patient CareQuantitative PET studies employing 1-[¹¹C]acetate and 1-[¹¹C]palmitate can employ venous blood samples for metabolite correction of an image-derived tracer arterial input function, thereby avoiding the risks of direct arterial blood sampling.     

14C]mechlorethamine binding to proteins of the human keratinocyte

Much mustard agent research has focused on mustard/DNA interactions. Mustard also interacts with proteins, however, and to reach the DNA any agent must first pass through the cytoplasm. We hypothesized that the cell's proteins would covalently bind mustard, and thereby limit its access to the DNA. Keratinocyte proteins were radiolabeled with [14C]mechlorethamine and separated by electrophoresis. The banding patterns that resulted were made visible on x-ray films, then compared with control patterns. A correspondence of almost one-to-one was observed, which supports the hypothesis that many cellular proteins are susceptible to mustard alkylation. It follows that some mustard symptoms probably result from effects on existing proteins.