Radioactivity In Mice Research Articles

Synthesis and evaluation of N-isopropyl-p-[11C]methylamphetamine as a novel cerebral blood flow tracer for positron emission tomography

IntroductionIncreases in fasting plasma glucose (PG) levels lead to a decrease in 2-deoxy-2-[18F]fluoro-d-glucose ([18F]FDG) uptake in the normal brain, especially in the precuneus, resulting in an Alzheimer’s disease (AD)-like uptake pattern. Therefore, patients with higher PG levels, such as those with diabetes, can be erroneously diagnosed with AD when positron emission tomography (PET) imaging is done using [18F]FDG, due to reduced uptake of [18F]FDG in the precuneus. To help avoid an erroneous diagnosis of AD due to differences in glucose metabolism, evaluating cerebral blood flow (CBF) in the brain is useful. However, current techniques such as single photon emission computed tomography (SPECT) and [15O]H2O PET have limitations regarding early diagnosis of AD because the images they produce are of low resolution. Here, we developed a novel CBF PET tracer that may be more useful than [18F]FDG for diagnosis of AD.MethodsWe synthesized and evaluated N-isopropyl-p-[11C]methylamphetamine ([11C]4) as a carbon-11-labeled analogue of the standard CBF SPECT tracer N-isopropyl-p-[123I]iodoamphetamine. Fundamental biological evaluations such as biodistribution, peripheral metabolism in mice, and brain kinetics of [11C]4 in non-human primates with PET with successive measurement of [15O]H2O were performed.Results[11C]4 was synthesized by methylation of the corresponding tributyltin precursor (2) with [11C]MeI in a palladium-promoted Stille cross-coupling reaction. The brain uptake of [11C]4 in mice peaked at 5–15 min after injection and then promptly decreased. Most radioactivity in the brain was detected in the unchanged form, although in the periphery, [11C]4 was rapidly metabolized to hydrophilic components. Acetazolamide (AZM) treatment significantly increased the brain uptake of [11C]4 without affecting the blood levels of radioactivity in mice. Preliminary kinetics analysis showed that the K1 of [11C]4 reflected regional CBF in a vehicle-treated monkey, but that the K1 did not reflect CBF in higher flow regions after AZM loading.Conclusion[11C]4 is a potential novel CBF PET tracer. Further validation studies are needed before [11C]4 can be used in humans.

Preclinical Comparison of Albumin-Binding Radiofolates: Impact of Linker Entities on the in Vitro and in Vivo Properties

Tumor targeting with folic acid radioconjugates has been proposed as a promising strategy for radionuclide therapy of folate receptor α (FR)-positive cancer. Recently, it was shown that modification of radiofolates with an albumin-binding entity increased the tumor-to-kidney ratios of accumulated radioactivity in mice. The goal of this study was to evaluate the lead compound cm10 and compare it with new albumin-binding folate conjugates. Compound cm12 was designed with a long spacer consisting of a PEG-11 entity, and compound cm13 contained a short alkane chain between the albumin-binding moiety and folic acid. All of the derivatives were labeled with 177Lu (t1/2 = 6.65 days, Eβ-,average = 134 keV; Eγ = 113 keV, 208 keV), a clinically established radionuclide for therapeutic purposes. The evaluation revealed that all of the albumin-binding radiofolates exhibited increased in vitro stability compared with the reference compound (177Lu-cm14) without albumin binder. Serum protein binding, determined with an ultrafiltration assay, was high (>88%) for the derivatives with albumin-binding entities. The FR-binding affinity was in the same range (KD = 4.0-7.5 nM) for all of the radiofolates, independent of the albumin-binding entity and spacer length. FR-specific uptake was proven in vitro using FR-positive KB tumor cells. In vivo studies with KB-tumor-bearing mice were performed in order to assess the tissue distribution profile of the novel radiofolates. 177Lu-cm13 showed high tumor uptake at late time points (13.3 ± 2.94% IA/g, 48 h p.i.) and tumor-to-kidney ratios (0.59 ± 0.03, 48 h p.i.) in the same range as 177Lu-cm10 (0.55 ± 0.07, 48 h p.i.). However, the tumor-to-kidney ratio of 177Lu-cm12 (0.28 ± 0.07, 48 h p.i.) was reduced compared with 177Lu-cm10 and 177Lu-cm13. The results of this study indicate that the spacer entity between folic acid and the albumin binder is of critical importance with regard to the tissue distribution profile of the radiofolate. The PEG spacer compromised the beneficial effects of the lead compound, but the design with a short alkane spacer appeared to be promising. Future studies will focus on the design of radiofolates with lipophilic and more rigid spacer entities, which may allow a further improvement of their tissue distribution profiles.

Evaluation of radioactivity in the bodies of mice induced by neutron exposure from an epi-thermal neutron source of an accelerator-based boron neutron capture therapy system.

This study aimed to evaluate the residual radioactivity in mice induced by neutron irradiation with an accelerator-based boron neutron capture therapy (BNCT) system using a solid Li target. The radionuclides and their activities were evaluated using a high-purity germanium (HP-Ge) detector. The saturated radioactivity of the irradiated mouse was estimated to assess the radiation protection needs for using the accelerator-based BNCT system. 24Na, 38Cl, 80mBr, 82Br, 56Mn, and 42K were identified, and their saturated radioactivities were (1.4 ± 0.1) × 102, (2.2 ± 0.1) × 101, (3.4 ± 0.4) × 102, 2.8 ± 0.1, 8.0 ± 0.1, and (3.8 ± 0.1) × 101 Bq/g/mA, respectively. The 24Na activation rate at a given neutron fluence was found to be consistent with the value reported from nuclear-reactor-based BNCT experiments. The induced activity of each nuclide can be estimated by entering the saturated activity of each nuclide, sample mass, irradiation time, and proton current into the derived activation equation in our accelerator-based BNCT system.

Studies on absorption, distribution and excretion of 14C labeled (+-)-7-(3-amino-1-pyrrolidinyl)-6-fluoro-1-(2,4-difluorophenyl)-1,4- dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acid p-toluene-sulfonate hydrate (14C-T-3262) in rats and mice

Absorption, distribution and excretion of T-3262 were studied in rats and mice after oral administration of 14C-T-3262. The obtained results are summarized as follows. 1. 14C-T-3262 was absorbed from the upper small intestine such as duodenum in rats. 2. Serum levels of radioactivity in rats reached the highest concentration at 1 hour after an oral administration, then gradually diminished. 3. Urinary excretion was 35% and 42% of the dosed radioactivity in rats and mice, respectively, and fecal excretion was about 65% and 56% of the dosed radioactivity in rats and mice, respectively. 4. Biliary excretion in rats was about 27% of the dosed radioactivity after an oral administration of 14C-T-3262, and a half amount of excreted radioactivity was reabsorbed from the intestine. 5. Radioactivity was distributed the most into the kidney and the liver among all organs other the stomach and the intestine. Radioactivity was widely distributed into other organs such as spleen, adrenal, pancreas, lung, heart and thymus. But the distribution of radioactivity into the brain was little. 6. The distribution of 14C-T-3262 was also studied with whole body autoradiography in normal male mice and pregnant mice. The radioactivity was distributed widely to whole tissues except brain, spinal cord and eye ball. In pregnant mice, radioactivity levels in the fetuses were the same as the blood level of the mother mice. 7. The binding rate of 14C-T-3262 to rats and mice serum proteins was 63-66%. 8. Urinary and fecal excretion patterns of radioactivity in mice after multiple oral administration of 14C-T-3262 for 10 days were similar to those after a single administration. This result suggests that T-3262 did not accumulate in body. 9. After oral administration of 14C-T-3262 to nursing rats, the secreted radioactivity level in the milk was higher than the blood level.

In Vitro and In Vivo Evaluation of a Novel 99mTc(CO)3-Pyrazolyl Conjugate of cyclo-(Arg-Gly-Asp-d-Tyr-Lys)

Radiolabeled peptides containing the Arg-Gly-Asp amino acid sequence (single letter code = RGD) have been studied extensively to target integrin receptors upregulated on tumor cells and neovasculature. Integrins are cell surface transmembrane glycoproteins that exist as alphabeta heterodimers. The alphavbeta3 integrin is known to be overexpressed in many tumor types and is expressed at lower levels in normal tissues. Furthermore, alphavbeta3 and alphavbeta5 subtypes are expressed in neovasculature during angiogenesis. Thus, there is some impetus to image angiogenesis and tumor formation in vivo using RGD-based peptide targeting vectors. In this study, we report the design and development of a new cyclic RGD analogue cyclo-[Arg-Gly-Asp-d-Tyr-Lys(PZ)] (PZ = 3,5-Me2-pz(CH2)2N((CH2)3COOH)(CH2)2NH2) that can be radiolabeled with the [99mTc(CO)3(H2O)3]+ metal aquaion. Radiochemical evaluation of this new conjugate in vitro indicated a facile radiosynthesis of the new 99mTc-RGD conjugate with high radiolabeling yields (>or=95%) and high specific activities. In vitro internalization and blocking assays in alphavbeta3 receptor-positive, human M21 melanoma cancer cells showed the ability of this conjugate to target the integrin receptor with high specificity and selectivity. In vivo pharmacokinetic studies in normal CF-1 mice showed rapid clearance from blood with excretion primarily via/through the renal-urinary system. In vivo accumulation of radioactivity in mice bearing either alphavbeta3 receptor-positive or negative human melanoma tumors showed receptor specific uptake of tracer with accumulations of 2.50 +/- 0.29 and 0.71 +/- 0.08% ID/g in alphavbeta3 integrin positive (M21) and negative (M21L) tumors at 1 h postinjection (p.i.), respectively.

A comparative evaluation of conventional and pretargeted radioimmunotherapy of CD20-expressing lymphoma xenografts

AbstractRadioimmunotherapy with anti-CD20 monoclonal antibodies is a promising new treatment approach for patients with relapsed B-cell lymphomas. However, the majority of patients treated with conventional radiolabeled anti-CD20 antibodies eventually have a relapse because the low tumor-to-blood and tumor-to–normal organ ratios of absorbed radioactivity limit the dose that can be safely administered without hematopoietic stem cell support. This study assessed the ability of a streptavidin-biotin “pretargeting” approach to improve the biodistribution of radioactivity in mice bearing Ramos lymphoma xenografts. A pretargeted streptavidin-conjugated anti-CD20 1F5 antibody was infused, followed 24 hours later by a biotinylated N-acetylgalactosamine–containing “clearing agent” and finally 3 hours later by 111In-labeled DOTA-biotin. Tumor-to-blood ratios were 3:1 or more with pretargeting, compared with 0.5:1 or less with conventional 111In-1F5. Tumor-to–normal organ ratios of absorbed radioactivity up to 56:1 were observed with pretargeting, but were 6:1 or less with conventional 111In-1F5. Therapy experiments demonstrated that 400 μCi (14.8 MBq) or more of conventional 90Y-1F5 was required to obtain major tumor responses, but this dose was associated with lethal toxicity in 100% of mice. In marked contrast, up to 800 μCi (29.6 MBq)90Y-DOTA-biotin could be safely administered by the pretargeting approach with only minor toxicity, and 89% of the mice were cured. These data suggest that anti-CD20 pretargeting shows great promise for improving current therapeutic options for B-cell lymphomas and warrants further preclinical and clinical testing.

A dual hypoxic marker technique for measuring oxygenation change within individual tumors

Rodent tumour models have been the 'workhorse' for tumour oxygenation research and for investigating radiobiological hypoxic fraction. Because of the intertumour heterogeneity of blood flow and related parameters, most studies have pooled information derived from several different tumours to establish the statistical significance of specific measurements. But it is the oxygenation status of and its modulation in individual tumours that has important prognostic significance. In that regard, the bioreducible hypoxic marker technique was tested for its potential to quantify oxygenation changes within individual tumours. Beta-D-iodinated azomycin galactoside (IAZG) and beta-D-iodinated azomycin xylopyranoside (IAZXP) were each radiolabelled with Iodine-125 and iodine-131 for measurements of animal tumour oxygenation. The tumour-blood (T/B) ratio of marker radioactivity in mice after the renal excretion of unbound marker (at 3 h and longer times) had been shown to be proportional to radiobiological hypoxic fraction. When markers labelled with both radioisotopes were administered simultaneously to EMT-6 tumour-bearing scid mice, T/B ratios were found to vary by up to 300% between different tumours, with an average intratumour variation of only approximately 4%. When the markers were administered 2.5-3.0 h apart, changes in T/B ratios of 8-25% were observed in 10 out of 28 (36%) tumours. Changes to both higher and lower hypoxic fraction were observed, suggestive of acute or cycling hypoxia. When 0.8 mg g(-1) nicotinamide plus carbogen was administered to increase tumour oxygenation, reductions in T/B ratios (mean deltaT/B approximately 38%) were observed in all tumours. Similar results were obtained with Dunning rat prostate carcinomas growing in Fischer x Copenhagen rats whose T/B ratios of IAZG and radiobiological hypoxic fractions are significantly lower. These studies suggest that fluctuating hypoxia can account for at least 25% of the total hypoxic fraction in some tumours and that correlations between bioreducible marker avidity and related tumour properties will be optimal when the independent assays are performed over the same time period. This dual hypoxic marker technique should prove useful for investigating both spontaneous and induced oxygenation changes within individual rodent tumours.

Radiolabeled metabolites of proteins play a critical role in radioactivity elimination from the liver

We have recently reported that the behavior of radiolabeled metabolites in the liver appears to be responsible for the hepatic radioactivity levels after administration of protein radiopharmaceuticals. To better understand the role played by radiolabeled metabolites in hepatic radioactivity levels, two benzyl-EDTA derivatives rendering different radiolabeled metabolites, 1-(4-isothiocyanatobenzyl) ethylenediaminetetraacetic acid (SCN-Bz-EDTA) and 1-[ p-(5-maleimidopentyl)aminobenzyl] ethylenediaminetetraacetic acid (ECMS-Bz-EDTA), were selected as bifunctional chelating agents (BCAs), and 111In labeling of galactosyl-neoglycoalbumin (NGA) and mannosyl-neoglycoalbumin (NMA) was performed. Biodistribution of radioactivity in mice and subcellular distribution of radioactivity in hepatocytes were then compared. After accumulation in hepatic parenchymal cells, NGA-EMCS-Bz-EDTA- 111 In rendered a faster elimination rate of radioactivity from the liver than NGA-SCN-Bz-EDTA- 111 In. Although each 111In-NMA exhibited a delayed elimination rate of radioactivity from the liver compared to the 111In-NGA counterpart, NMA-EMCS-Bz-EDTA- 111In showed faster elimination rate of radioactivity than NMA-SCN-Bz-EDTA- 111In. Analyses of radioactivity excreted in feces and urine and remaining in the liver indicated that both BCAs rendered mono-amino acid adducts as the major radiolabeled metabolites (cysteine-EMCS-Bz-EDTA- 111In and lysine-SCN-Bz-EDTA- 111In), which were generated in both cell types of the liver within 1 h postinjection. Subcellular distribution of radioactivity indicated that the radioactivity was copurified with lysosomes. These results demonstrate that although in vivo stability of radiometal chelates is essential, the biological properties of the radiolabeled metabolites generated after lysosomal proteolysis in hepatocytes play a critical role in radioactivity elimination from the liver.

New azomycin acyclonucleoside. Synthesis and biodistribution of radiohalogenated analogues in tumor‐bearing mice

AbstractThe design, synthesis and biological activities of several acyclonucleoside analogues related to misoni‐dazole are described. The hydroxy‐5, bromo‐6, iodo‐7, and fluoro‐8 derivatives of ethoxymethylazomycin and iodopropenyloxymethylazomycin (12) have been prepared. Alkylation of silylated azomycin with haloethoxy‐methylene chloride gave the corresponding acyclonucleosides. Similarly, propargyloxymethylene chloride gave propargyloxymethylazomycin (10), which after hydrostannylation and subsequent iododestannylation yielded iodopropenyloxymethylazomycin (12). The radiolabeled [125I] or [18F] compounds were prepared from the corresponding substrates. Biodistribution results of the radiolabeled analogues in mice showed that compound 7 had good tumor uptake (2.0% injected dose/g at 1 hour). The high radioactive levels in blood and stomach, however, were perhaps due to in vivo deiodination or metabolism. Compound [125I]‐12 showed the highest tumor uptake (4.8 and 3.6% injected dose/g at 1 and 4 hours respectively) of all of the compounds tested. Relatively low thyroid uptake of radioactivity in mice dosed with compound [125I]‐12 indicates significantly reduced in vivo deiodination in comparison to compound [125I]‐7.

In vivo biodistribution of two [ 18F]-labelled muscarinic cholinergic receptor ligands: 2-[ 18F]- and 4-[ 18F]-fluorodexetimide

Two [ 18F]-labelled analogues of the potent muscarinic cholinergic receptor (m-AChR) antagonist, dexetimide, were evaluated as potential ligands for imaging m-AChR by positron emission tomography (PET). Intravenous administration of both 2-[ 18F]- or 4-[ 18F]- fluorodexetimide resulted in high brain uptake of radioactivity in mice. High binding levels were observed in m-AChR rich areas, such as cortex and striatum, with low levels in the receptor-poor cerebellum. Uptake of radioactivity was saturable and could be blocked by pre-administration of dexetimide or atropine. Drugs with different sites of action were ineffective at blocking receptor binding. The results indicate that both radiotracers are promising candidates for use in PET studies.

Radioimmunotherapy of human colon carcinoma by 131I-labelled monoclonal anti-CEA antibodies in a nude mouse model.

A mixture of 3 MAbs directed against 3 different CEA epitopes was radiolabelled with 131I and used for the treatment of a human colon carcinoma transplanted s.c. into nude mice. Intact MAbs and F(ab')2 fragments were mixed because it had been shown by autoradiography that these 2 antibody forms can penetrate into different areas of the tumor nodule. Ten days after transplantation of colon tumor T380 a single dose of 600 microCi of 131I MAbs was injected i.v. The tumor grafts were well established (as evidenced by exponential growth in untreated mice) and their size continued to increase up to 6 days after radiolabelled antibody injection. Tumor shrinking was then observed lasting for 4-12 weeks. In a control group injected with 600 microCi of 131I coupled to irrelevant monoclonal IgG, tumor growth was delayed, but no regression was observed. Tumors of mice injected with the corresponding amount of unlabelled antibodies grew like those of untreated mice. Based on measurements of the effective whole-body half-life of injected 131I, the mean radiation dose received by the animals was calculated to be 382 rads for the antibody group and 478 rads for the normal IgG controls. The genetically immunodeficient animals exhibited no increase in mortality, and only limited bone-marrow toxicity was observed. Direct measurement of radioactivity in mice dissected 1, 3 and 7 days after 131I-MAb injection showed that 25, 7.2 and 2.2% of injected dose were recovered per gram of tumor, the mean radiation dose delivered to the tumor being thus more than 5,000 rads. These experiments show that therapeutic doses of radioactivity can be selectively directed to human colon carcinoma by i.v. injection of 131I-labelled anti-CEA MAbs.

Percutaneous absorption of [14C]methacrylamide in animals

Percutaneous absorption of [14C]methacrylamide was determined in rabbits, rats and mice. Radioactivity in blood of rabbits increased rapidly after IV injection, after topical application with a cloth and after direct topical application of a 15 or 5% test solution, suggesting high permeability of the skin for methacrylamide. Radioactivity then began to decrease exponentially within 1 h. Tissue radioactivity 24 h after IV dosing was high in blood, liver and serum, and low in brain, nerve and muscle. The radioactivity was more uniformly distributed with the exception of liver, after application with a cloth and after direct contact than after IV dosing. When the application site was washed with water after direct application, decline of radioactivity in blood was accelerated slightly and a decrease in radioactivity in some tissues was found, although the difference between non-wash and wash groups was not significant in either the declining curve or the tissue radioactivity, with the exception of serum for the latter. Between 25 and 60% of the radioactivity found in tissues was protein-bound after 24 h. Recovery of radioactivity in urine was highest after IV administration, intermediate after direct contact, and lowest after cloth application. Radioactivity in expired air and bile was small. Both radioactivity in tissues and its recovery in urine in rats, and tissue radioactivity in mice, were lower than in rabbits, when adjusted for dose per unit body weight, suggesting lower skin permeability for methacrylamide in the former species.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence that 1-naphthol is not an obligate intermediate in the covalent binding and the pulmonary bronchiolar necrosis by naphthalene

Recent studies of a number of volatile aromatic hydrocarbons have suggested that the formation of covalently bound metabolites arises solely through the intermediate formation of phenols. This study further examines the involvement of 1-naphthol in the in vivo and in vitro formation of covalently bound metabolites and pulmonary bronchiolar necrosis by naphthalene. Marked differences were observed in the rate of 1-naphthol formation in lung and liver microsomal incubations without correspondingly large differences between the rates of formation of covalently bound metabolites from naphthalene and 1-naphthol. Glutathione decreased covalent binding in hepatic microsomal incubations containing 14[C]1-naphthol but did not result in the formation of any of the glutathione adducts isolated from identical incubations containing 14[C]naphthalene. Tissue levels of covalently bound radioactivity in mice treated with 14[C]1-naphthol or 14[C]naphthalene were similar; however, in contrast to studies with naphthalene, 1-naphthol administration did not deplete tissue glutathione nor result in detectable tissue injury. These studies indicate that 1-naphthol is not an obligate intermediate in the formation of covalently bound metabolites from naphthalene nor does it appear to be a more proximate lung toxic metabolite.

Enzymatic syntheses of phosphate, l-citrulline, and N-carbamyl l-aspartate labeled with either 13N or 11C

[ 13N]- and [ 11C]carbamyl phosphate, l-[ω- 13N]citrulline, l-[ ureido- 11C]citrulline, [ carbamyl- 13N]- and [ carbamyl- 11C]carbamyl- l-aspartate were synthesized using carbamyl phosphate synthetase coimmobilized with either aspartate transcarbamylase or ornithine transcarbamylase. Carbamyl l-[ 13N]aspartate was enzymatically prepared from carbamyl phosphate and l-[ 13N]aspartate. The tissue distribution of radioactivity in mice after injection of radiolabeled ammonia, carbamyl phosphate or citrulline was studied. The tissue distribution of isotope derived from [ 13N)carbamyl phosphate and [ 13N]ammonia were similar, with the exception of liver, brain and pancreas, in which 13NH 3 uptake was higher after retroorbital injection. The distribution of label derived from l-[ω- 13N]- and l-[ ureido- 13C]citrulline was similar. Substantial tumor (Sarcoma-180) uptake of label from l-citrulline was observed.

Pitfalls in the interpretation of whole-body autoradiograms: long-time retention in brain and adrenal cortex caused by metabolic incorporation of 14C from various labelled xenobiotics.

The long-time retention of radioactivity in mice was studied by whole-body autoradiography after administration of 1-14C-alkanes (C12 and C16), 1-14C-polychlorododecanes (56 and 68% Cl w/w), U-14C-polychlorohexadecane (23% Cl w/w), ethyl-14C-phenacetin and ring-3H-phenacetin. All the labelled xenobiotics, except the high-chlorinated (68% Cl) polychloroalkane and the ring-3H-phenacetin, gave rise to long-time (12-60 days) retention of radioactivity in the central nervous system and in the adrenal cortex; the distribution of radioactivity within the brain corresponded to the stain intensity of myelin stained sections. Administration of 1-14C-fatty acids (C12 and C16) and 1-14C-acetylcoenzyme A gave a similar distribution pattern. The lipophilic radioactivity in brain and adrenal tissue was extracted and separated with thin-layer chromatography. In the adrenal extracts, the label co-chromatography mainly with cholesteryl ester, and in the brain extracts with cholesterol and with more polar lipids (mainly phosphatidyl-choline and -ethanolamine). The brain homogenate contained a non-extracted, probably proteinaceous, residue, with comparably high radioactivity. The results show that several 14C-labelled xenobiotics which give long time retention of radioactivity in the adrenal cortex and brain, are degraded to intermediates with the possibility to become incorporated into endogenous substances. The high-chlorinated alkane (1) and ring-3H-phenacetin (2) did not give such long time retention due to its persistance towards degradation (1), and lack of labelling of the degradable part of the molecule (2). It is concluded that erroneous interpretations can be drawn from distribution studies if the routes of degradation and positions of label of the 14C-labelled compounds are not considered.

Radioactive metal complexes of ethylenediamine-N,N-diacetic acid. Biodistribution of radioactivity in mice bearing tumors.

Complexes of ethylenediamine-N, N-diacetic acid (EDDA) with radioactive metal ions and 3H-labeled EDDA were prepared and the biodistribution of the radioactivity in mice bearing Ehrlich tumor was studied. Radioactive complexes studied were those of 51Cr, 57Co, 59Fe, 64Cu, and 67Ga. μ-Oxo 57Co EDDA was prepared by treatment of 57Co EDDA with hydrogen peroxide. The tumor/blood ratios of radioactivity indicated that 57Co EDDA and μ-oxo 57Co EDDA were concentrated in the tumor tissues, whereas other complexes and 3H-EDDA were not. The tumor tissues were clearly visualized in scintigrams after the administration of the 57Co complexes to mice.

The effects of α-tocopherol on the toxicity, disposition, and metabolism of adriamycin in mice

Fourteen days after adriamycin treatment, 15 mg/kg ip, there was greater than 50% mortality in CDF 1 mice pretreated with either olive oil or saline ip, but only 5% mortality in animals pretreated with a single dose of α-tocopherol. However, 60 days after adriamycin, mortality was 80±5% in all three groups. A single dose of α-tocopherol alone caused no deaths. Blood concentrations of [ 14C]adriamycin-derived radioactivity in mice pretreated with α-tocopherol of olive oil were significantly higher than those of saline controls between 3 and 15 min after injection. At 30 and 60 min blood concentrations of radioactivity did not differ in the three groups. Sixty minutes after adriamycin administration, concentrations of radioactivity in heart, kidney, muscle, and lung were significantly higher in the α-tocopherol and olive oil groups than in the saline controls. No differences in the metabolic profile of adriamycin were found in heart or liver, but renal concentration of adriamycin and several metabolites were higher in both the α-tocopherol and olive oil groups. In general, α-tocopherol pretreatment had only slight effect on the metabolism of adriamycin in vivo. Thus, the time-dependent efficacy of α-tocopherol in ameliorating the lethal toxicity of adriamycin in mice does not appear to result from acute changes in the distribution or metabolism of adriamycin. It appears that the effect of α-tocopherol is to delay rather than prevent the lethal toxicity of adriamycin.

Gastrointestinal absorption and organ distribution of oral cadmium chloride and cadmium-metallothionein in mice.

Body retention and tissue distribution of Cd from oral 109CdCl2 and 109Cd-metallothionein were studied in C57BL/6J mice given identical doses (60 microgram Cd and 2 muCi 109Cd). Measurement of 109Cd radioactivity in mice showed identical absorption but differences in tissue distribution of Cd from the two forms. A significantly greater deposition of Cd was observed in the kidney of mice fed Cd-metallothionein than in the CdCl2 group where a major portion of Cd was deposited in the liver. Most of the radioactive Cd in the renal and hepatic tissue and in the duodenum was bound to metallothionein 24 h after oral Cd-metallothionein, whereas only 30 and 38% of the cadmium in liver and kidney supernatants, respectively, were bound to metallothionein after oral CdCl2. These results suggest that the dietary form of Cd may influence the renal deposition of Cd.

Studies on the Fate of Poisonous Metals in Experimental Animal (VIII)

About 30-60μCi/0.15mg Cd/kg of cadmium chloride solution containing 115mCd was injected intraperitoneally to mice, rats, guinea pigs, rabbits and quails, and thereafter the whole body retention of Cd was measured continuously for 60-92 days in order to find the biological half lives of the metal in these animals. The whole body retention was determined by whole body counting of radioactivity in mice, rats, guinea pigs and quails, but in the case of rabbit it was determined by counting rates of excreta.The biological half lives thus obtained in mouse, rat, guinea pig, rabbit and quail were 220, 150 and 181, 334, 299 and 367 days, respectively. Namely, an apparent species difference was observed even under the same conditions such as sex of animal, dose of metal per kg and dosing route.

Tissue distribution and binding of radioactivity in mouse after intravenous administration of [14C]3-chloro-p-toluidine.

The avicide [14C]3-chloro-p-toluidine (CPT) HCL, ring labeled, was injected intravenously to mice. The radioactivity associated with this compound was found to be unevenly distributed in different parts of the body. It leaves the plasma, as well as many tissues, with 2 elimination rate constants, the fast and the slow. The faster component of the [14C]CPT decay curve of the plasma was similar to the faster components of the decay curves of brain, lung, heart, intestine, testicle and kidney. The retention half-life of the radioactivity for the slower component of the decay curve varied a great deal from tissue to tissue, being shortest (14.55 h) in the intestine and longest (326 h) in the adipose tissue. Of the 10 tissues examined, a substantial amount of [14C]CPT radioactivity was found to be covalently bound only to liver, kidney, lung and RBC protein. There was no cause and effect relationship between the covalent binding of radioactivity and the tissue pathology, since no remarkable histopathological lesions were found in the liver and kidney of treated mice. The tissue retention of [14C]CPT radioactivity did not parrallel the covalent binding of the compound to tissue protein. The covalent binding of [14C]CPT radioactivity to RBC was suggestive of the conversion of the parent compound into a reactive metabolite responsible for the generation of methemoglobin in mice. The percent distribution of radioactivity in subcellular fractions of liver and kidney correlated with the amount of protein associated with subcellular fractions. The 102 000 g supernatant fraction of the liver contained the highest proportion of radioactivity, both in terms of absolute percent radioactivity as well as specific activity (dpm/mg of protein). This was also true for the 102 000 g supernatant fraction of the kidney. The majority of radioactivity in the 102 000 g supernatant fraction of liver appears to be bound to one or more polypeptide sized proteins with a mol. wt. of approx. 1000--2000.