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Y Fujibayashi

Publications and source records attributed to Y Fujibayashi.

At least 55 records · Page 3Linked to original sources
PubMed1998

Intracellular metabolism of 99mTc-d,l-HMPAO in vitro: a basic approach for understanding the hyperfixation mechanism in damaged brain.

The mechanism of technetium-99m-labeled d,l-hexamethylpropylene amine oxime (99mTc-HMPAO) hyperfixation in damaged brain was elucidated using in vitro metabolic studies. Among the subcellular fractions of mouse brain homogenate, the mitochondrial fraction showed dominant metabolic activity with respect to 99mTc-HMPAO, followed by the cytosolic fraction. The metabolic activity of the mitochondrial fraction was enhanced by heat and detergent treatment, being proportional to the leakage of thiol (SH) compound(s) from the granules. The leaked SH compound(s) had a higher metabolic activity than glutathione, a well-known reductant in cells. 99mTc-HMPAO might be metabolized by mitochondrial SH compound(s) exhibiting strong reductant activity, and hyperfixation might be an indication of mitochondrial damage of the brain.

Animals↗
PubMed1998

The importance of glucose transport activity as the rate-limiting step of 2-deoxyglucose uptake in tumor cells in vitro.

Glucose transporter (GLUT) expression and hexokinase activity are thought to be related to high [18F]-fluorodeoxyglucose (FDG) uptake in tumor cells, but their relative importance is still unknown. To determine which is the predominant factor in FDG uptake in tumor cells, cultured tumor cell lines and a normal cell line were studied in vitro with respect to 2-deoxyglucose (DG) uptake, hexokinase activity, and the initial uptake rate of 3-O-methylglucose (3-O-MG) transport, which is generally accepted as indicating the amount of GLUT expressed on the plasma membrane. In 16 types of tumor cells and one fibroblast cell line, DG uptake was assessed for 60 min, the initial uptake rate of 3-O-MG transport was measured for 1 min, and total hexokinase activity, including that in the mitochondrial fraction, was determined. Across all 16 tumor cell lines, there was a significant correlation between DG uptake and 3-O-MG transport (p = 0.0012, F test), but not between DG uptake and hexokinase activity. Hexokinase activity of the tumor cells was comparable to that of the human fibroblast cells in the exponential growth phase. Most tumor cells showed higher DG uptake and 3-O-MG transport than the human fibroblast cells. The results suggest that DG uptake of cultured tumor cells is governed by GLUT expression, which may be a distinct characteristic of the neoplastic process.

3-O-Methylglucose↗
PubMed1998

Glucose transporter protein-independent tumor cell accumulation of fluorine-18-AFDG, a lipophilic fluorine-18-FDG analog.

UNLABELLED: Fluorine-18-fluorodeoxyglucose (FDG) is used clinically for tumor diagnosis, but its mechanism of accumulation in tumor cells is complicated because two factors, glucose transporter protein (GLUT) and hexokinase, govern [18F]FDG uptake directly. We selected a lipophilic [18F]FDG analog, 1,3,4,6-tetra-acetyl-2-[18F]-2-deoxy-D-glucose ([18F]AFDG), to regulate the effects of hexokinase and evaluated its characteristics in an in vitro cell culture system. METHODS: Fluorine-18-AFDG was synthesized by the method used to produce [18F]FDG, as an intermediate of [18F]FDG. Fluorine-18-AFDG uptake study was performed with LS180 tumor cells, and its metabolites were also investigated by thin-layer chromatography. To evaluate the relationship between [18F]AFDG and GLUT, we also examined [18F]AFDG uptake in the presence of cytochalasin B or with increased medium glucose concentration. The effects of lowered temperature (4 degrees C) on [18F]AFDG uptake were also investigated. RESULTS: Fluorine-18-AFDG (lipophilicity: octanol/water = 3.5) uptake was 3.3-fold higher than that of [18F]FDG. Metabolic analysis showed that [18F]AFDG was extremely stable in the incubation medium but was quickly hydrolyzed and metabolized to 2-fluoro-[18F]-2-deoxy-D-glucose-6-phosphate ([18F]FDG-6P) in tumor cells. Fluorine-18-FDG-6P accounted for approximately 45% of the total radioactivity after a 60-min incubation of [18F]AFDG. Incubation with 50 microM cytochalasin B did not affect [18F]AFDG uptake. In medium with double the control glucose level, [18F]FDG uptake was decreased by about 50%, but [18F]AFDG uptake was not affected. Fluorine-18-AFDG uptake and [18F]FDG-6P production did not show saturation and increased linearly with addition of a 10-fold higher concentration of [18F]AFDG. Lowered incubation temperature caused decreased [18F]AFDG uptake due to reduced [18F]FDG-6P production. CONCLUSION: Fluorine-18-AFDG rapidly penetrated the cell membrane as a result of its high lipophilicity and was metabolized to [18F]FDG-6P within cells. Fluorine-18-AFDG was thus characterized as "GLUT-independent [18F]FDG."

Cytochalasin B↗
PubMed1998

Effect of metabolic substrate on BMIPP metabolism in canine myocardium.

UNLABELLED: The lipid tracer 1 5-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (BMIPP) is clinically useful, and its basic metabolism is being analyzed. Because the pharmacokinetics of this lipid tracer may be affected by blood concentrations of fatty acid or glucose, this study evaluated the effects of excess levels of lipid or glucose on BMIPP uptake and metabolism. METHODS: A technique using an open-chest dog model was used. Blood sampling was performed from the left anterior descending coronary artery and great cardiac vein after an injection of 123I-BMIPP either with a glucose infusion (n = 6) or a lipid infusion (n = 5). High performance liquid chromatography and double-tracer kinetic analyses clarified the extraction, retention, backdiffusion and further metabolism of BMIPP. These results were compared with data from control dogs (n = 6). RESULTS: In this experiment, a 10-fold increase over the normal lipid blood concentration and twofold increase over the normal blood glucose concentration were evaluated with either intralipid or glucose infusion, respectively. In the lipid infusion studies, the extraction significantly decreased compared with the control values (74% +/- 12% to 58% +/- 8%; p < 0.05), and the washout increased from 50% +/- 13% to 68% +/- 16% (p < 0.05). The BMIPP backdiffusion increased (p < 0.05), and the levels of the further metabolites decreased (p < 0.05), while the retention level remained constant (normal, 89% +/- 9%; lipid infusion, 91% +/- 3%; ns). In the glucose infusion studies, the BMIPP extraction, retention and washout showed no statistical differences compared to controls; however, these parameters showed the same tendencies as those in the lipid infusion group. In addition, the BMIPP backdiffusion increased significantly (control, 25.1% +/- 8%; glucose infusion, 48.7% +/- 25.6%; p < 0.05) as it did after the lipid infusion. CONCLUSION: BMIPP metabolism and uptake are affected by excess concentrations of lipid and glucose in the blood. However, the retention of BMIPP was not affected by either type of infusion. The BMIPP backdiffusion and the further metabolite comprising 10% of the tracer extracted were affected both by the lipid and glucose infusions. These results indicate that an excess fat concentration and glucose affect BMIPP uptake, especially the extraction of BMIPP and BMIPP backdiffusion.

Animals↗
PubMed1998

Distribution of glutathione and technetium-99m-meso-HMPAO in normal and diethyl maleate-treated mouse brain mitochondria.

UNLABELLED: The aim of this study was to explain the contribution of mitochondria to the accumulation of 99mTc-meso-hexamethyl propyleneamine oxime (HMPAO) in the brain, after examinations were performed. METHODS: We studied subcellular distribution of 99mTc-meso-HMPAO and glutathione (GSH) in normal and diethyl maleate (DEM)-administered mice. RESULTS: In normal brain, major radioactivity was found in the mitochondrial (49.0%) and cytosolic fractions (33.0%), while the GSH content was high in the cytosol (63.2%) and mitochondria (30.6%). The radioactivity in mitochondrial, cytosolic, microsomal and nuclear fractions was decreased in a dose-dependent manner by DEM, a GSH depleting agent, to 32.2% (mitochondrial) and 24.7% (cytosolic) of the control by a dose of 550 mg/kg. The GSH content in mitochondrial and cytosolic fractions also decreased in a dose-dependent manner on DEM treatment to 29.3% (mitochondrial) and 30.0% (cytosolic) of the control by 550 mg/kg of DEM. A good correlation was found between the uptake of 99mTc-meso-HMPAO and GSH content in mitochondrial, cytosolic and nuclear fractions, with a correlation coefficient (r) of 0.814, 0.834 and 0.784, respectively. CONCLUSION: Mitochondria are a major subcellular fraction for the uptake of 99mTc-meso-HMPAO by the brain, and GSH in mitochondria contributes to the accumulation of 99mTc-meso-HMPAO.

Animals↗
PubMed1997

Effects of antitumor agents on 3H-2-deoxyglucose uptake in tumor cells and their relationship with the main targets of the antitumor agents.

To investigate the effects of antitumor drugs on 3H-2-deoxyglucose (DG) uptake in tumor cells, we performed DG uptake studies of the short-term treatment of four kinds of antitumor drugs in a cell culture system. The antitumor drugs adriamycin (ADM) and cisplatin (cDDP), which affect on DNA synthesis, did not greatly affect DG uptake, but DG uptake was lowered by antitumor drugs, actinomycin D (AcD) and cycloheximide (CHX), which target the gene expression system. To investigate the mechanism of DG uptake changes, we also tested the effects of some glucose metabolic inhibitors on DG uptake. An inhibitor of glycolytic flow (iodoacetate) lowered DG uptake whereas mitochondrial inhibition increased DG uptake. These results on the inhibition of glucose metabolism indicated that there were two types of factors affecting DG uptake directly; one affects glycolysis and the other affects oxidative phosphorylation. The two antitumor drugs with effects on gene expression were thought to act by the former. The effects of the drug treatments for tumors on DG uptake could be divided into three groups; glycolysis inhibition, mitochondrial inhibition and no relation to glucose metabolism. With the further observations of FDG uptake changes based on this prediction, the biochemical relationship between treatment effects and FDG uptake changes will be clarified.

2,4-Dinitrophenol↗
PubMed1997

Radioiodinated alpha-p-iodophenyl-N-tert-butylnitrone as a radical detecting agent in vivo.

For in vivo detection of unstable radical species, a novel radioiodinated radical trapping agent, alpha-p-iodophenyl-N-tert-butylnitrone (IPBN), was designed based on the plausible characteristics of alpha-p-hydroxy-m-iodophenyl-N-tert-butylnitrone (HIPBN). Both compounds are iodinated analogs of alpha-phenyl-N-tert-butylnitrone (PBN), but the latter showed low stability in vivo. The present compound IPBN was easily prepared and labeled with radioiodine. It showed very stable characteristics in vitro as well as in vivo, but was easily metabolized and retained at sites of superoxide production.

Animals↗
PubMed1997

Reassessment of FDG uptake in tumor cells: high FDG uptake as a reflection of oxygen-independent glycolysis dominant energy production.

To determine appropriate use of 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) in the diagnosis of malignant tumors, the mechanism of enhanced FDG uptake in tumor cells was reassessed using in vitro cultured cell lines and 3H-deoxyglucose (DG), in combination with possible parameters of aerobic and anaerobic energy production. The high DG uptake in the tumor cells reflected the dependency of energy production on anaerobic glycolysis, and paradoxically on low levels of aerobic oxidative phosphorylation in mitochondria. We discuss here factors underlying anaerobic glycolysis in tumor cells.

Adenosine Triphosphate↗
PubMed1997

Transient increase in glycolytic metabolism in cultured tumor cells immediately after exposure to ionizing radiation: from gene expression to deoxyglucose uptake.

The transient change in uptake of deoxyglucose (DG) and expression of glycolysis-associated gene products in cultured tumor cells (LS180 human colon adenocarcinoma cells) immediately after single-dose X irradiation were examined to acquire basic data for use in the early assessment of tumor responses to radiation treatment by position emission tomography. An increase in accumulation of DG was found 3-5 h postirradiation. Inhibitors of both mRNA and protein synthesis and glycoprotein transport suppressed the increase in accumulation of DG to the control level. Both the glucose transporter-1 mRNA expression and the enzymatic activity of hexokinase in the cells were significantly elevated in conjunction with high DG accumulation. These findings indicate that the transiently elevated glucose metabolism occurred via processes at the levels of gene expression. These transient tumor cell responses might be useful for the early assessment of radiation damage.

Colonic Neoplasms↗
PubMed1997

Hyperfixation of copper-62-PTSM in rat brain after transient global ischemia.

UNLABELLED: We evaluated the regional distribution of 62Cu-pyruvaldehyde bis(N4-methylthiosemicarbazone) (62Cu-PTSM), a potential PET perfusion agent, in the rat brain and observed hyperfixation in transient global ischemia in rats. METHODS: The distribution of 62Cu-PTSM was examined in comparison with that of 123I-labeled p-iodophenyl-N-isopropylmethanphetamine (123I-IMP) as a reference blood flow marker. Brain uptake of these two tracers was measured in Wistar rats subjected to 30-min four-vessel occlusion followed by recirculation for 10 min, 1 hr or 1, 3 or 5 days. Tracers were injected intravenously into rats 10 min before decapitation. The activities of Complex I and Complex I-III of mitochondria and the concentration of sulfhydryl (SH) groups were also measured. RESULTS: Copper-62-PTSM showed accelerated accumulation in the brain at 1 hr and 1 day after reperfusion when compared with that of 123I-IMP (p < 0.01), and this enhancement was considered to be due to hyperfixation. At these time points, SH concentration was significantly decreased (p < 0.01). On the other hand, the activity of Complex I was not influenced by ischemia/reperfusion, but that of Complex I-III was decreased to 65-70% of the control level (p < 0.01). CONCLUSIONS: Copper-62-PTSM showed hyperfixation most possibly as a result of increased NADH concentration, caused by disturbed electron transport in mitochondria.

Animals↗
PubMed1997

Copper-62-ATSM: a new hypoxia imaging agent with high membrane permeability and low redox potential.

UNLABELLED: An ideal hypoxia imaging agent should have high membrane permeability for easy access to intracellular mitochondria and low redox potential to confer stability in normal tissue, but it should be able to be reduced by mitochondria with abnormally high electron concentrations in hypoxic cells. In this context, nitroimidazole residues are not considered to be essential. In this study, Cu(II)-diacetyl-bis(N4-methylthiosemicarbazone) (Cu-ATSM), a 62Cu-bisthiosemicarbazone complex, with high membrane permeability and low redox potential, was evaluated as a possible hypoxia imaging agent, using electron spin resonance spectrometry and the Langendorff isolated perfused rat heart model as well as rat heart left anterior descending occlusion model. METHODS: Nonradioactive Cu-ATSM was incubated with rat mitochondria, after which reduction of Cu(II) to Cu(I) was measured with electron spin resonance. As a model of hypoxic mitochondria, rotenone (Complex I inhibitor)-treated mitochondria were used. RESULTS: In this study, Cu-ATSM was reduced by hypoxic but not by normal mitochondria. CONCLUSION: Thus, retention of 62Cu-ATSM was studied serially in perfused rat hearts under conditions of normoxia (95% O2 + 5% CO2), hypoxia (95% N2 + 5% CO2) and reoxygenation (95% O2 + 5% CO2). In normoxia and reoxygenation, 62Cu-ATSM injected as a single bolus showed low retention (23.77% and 22.80%, respectively) 15 min after injection, but retention was increased markedly under hypoxic conditions (81.10%). Also, in the in vivo left anterior descending occluded rat heart model, 62Cu-ATSM retention was inversely correlated with accumulation of 201Tl, a relative myocardial blood flow marker.

Animals↗
PubMed1997

Myocardial kinetics of iodine-123-BMIPP in canine myocardium after regional ischemia and reperfusion: implications for clinical SPECT.

UNLABELLED: To evaluate the clinical utility of 123I-(rho-iodophenyl)-3-R,S-methylpentadecanoic acid (123I-BMIPP) for ischemic heart disease, we investigated the metabolic fate of 123I-BMIPP in canine models with mild and severe ischemia and evaluated the clinical utility of this tracer. METHODS: Using open-chest dogs under anesthesia, we assembled a system that would release all the blood from the great cardiac vein without recirculation, if necessary. After injection of BMIPP into the left anterior descending coronary artery, blood samplings from cardiac vein and abdominal aorta were performed for 10-min ischemia (mild ischemia, five dogs) and 30-min ischemia (severe ischemia, six dogs), after reperfusion and for normal controls (six dogs). The catabolites of BMIPP, including backdiffusion of nonmetabolized BMIPP, were evaluated using high-performance liquid chromatography. RESULTS: Although the rapid extraction of BMIPP from the plasma into the myocardium and the subsequent retention were unchanged among three groups, the early washout (at 8 min) of radioactivity significantly increased (from 50% +/- 13% to 61% +/- 8%; p < 0.05) in severe ischemia. The metabolites from the myocardium consisted of backdiffusion of nonmetabolized BMIPP and alpha-oxidation, intermediate-oxidation and full-oxidation metabolites. For mild ischemia, these values were not significantly changed from the normal control, although the respective proportions of metabolites showed some variation. Lactate production after reperfusion on mild ischemia, which indicates the severity of ischemia, was closely correlated with the level of backdiffusion of BMIPP (r = -0.92) and the full-oxidation metabolite (r = 0.78). On the other hand, for severe ischemia, the level of backdiffusion of nonmetabolized BMIPP increased (from 25.1% +/- 8.0% to 34.7% +/- 8.7%; p < 0.05), and the full-oxidation metabolites decreased (from 21.4% +/- 10.9% to 14.8% +/- 7.3%). CONCLUSION: The metabolism of BMIPP was closely associated with the severity of myocardial ischemia. Thus, 123I-BMIPP might be a promising and sensitive radiopharmaceutical for the evaluation of ischemic heart disease.

Animals↗
PubMed1996

Applicability of short-lived radiometallic nuclide for high sensitivity two-site "sandwich" immunoradiometric assay: human growth hormone assay.

The sensitivity of the IRMA method is limited by the specific activity (SA) of the conventionally employed radioisotropic label and high sensitivity radioimmunoassay should theoretically be attained by the use of short-lived radiometallic nuclides. Our group have achieved radiolabeling of high SA IgG by using the radiometal, gallium-67 (67Ga) with a short half-life (T1/2 = 78 h) and deferoxamine (DF), a bifunctional chelating agent bound through a multispacer (dialdehyde starch, DAS) as the linker (J Nucl Med 32:825, 1991). In the present work, the application of the approach is attempted by employing a two-site IRMA for human growth hormone (hGH); the monoclonal antibody to hGH (MAB2) is bound to DF via DAS and the coupled DF-DAS-MAB2 is radiolabeled with 67Ga. The 67Ga-DF-DAS-MAB2 of high SA (4,884 MBq/mg versus 370-518 MBq/mg calculated for radioiodinated MAB2) was thus used for the two site 'sandwich' 67Ga-IRMA. Excellent correlation with the 125I-IRMA was registered, and higher detection capability obtained by using 67Ga over the 125I in the hGH IRMA offered a good basis for the exploitation of short-lived radio-nuclides in the IRMA system.

Antibodies, Monoclonal↗
PubMed1996

Evaluation of myocardial viability with iodine-123-BMIPP in a canine model.

UNLABELLED: The tracer 123I-BMIPP was examined for its ability to reflect myocardial lipid metabolism. Studies in mice indicate that myocardial BMIPP uptake correlates with ATP content. Details, however, of myocardial accumulation in the ischemic period with either infarct or ischemia are not well documented. METHODS: Sixteen adult mongrel dogs were investigated. The occluded left anterior descending artery (LAD) alone was reperfused to make the ischemic area, and the first diagonal branch of the LAD was kept occluded to make the infarct area. Regional wall motion was evaluated by echocardiography in the short-axial view from the epicardium. Tissue blood flow was calculated using nonradioactive colored microspheres. Changes in blood glucose levels, lipid levels and lactate extraction were examined in blood collected from the aorta and great cardiac vein (GCV). The ATP concentration and BMIPP count were determined by high-performance liquid chromatography and gamma-counter, respectively. RESULTS: Two hours after reperfusion, blood flow decreased to 20% +/- 5% in the infarct area and 64% +/- 9% in the ischemic area (p < 0.05), despite comparable wall-motion reduction (32% +/- 5% and 42% +/- 12% in the infarct and ischemic areas, respectively). BMIPP content and ATP concentration showed parallel reduction: 40% +/- 7% and 75% +/- 4% (p < 0.05) of BMIPP and 32% +/- 9% and 69% +/- 7% (p < 0.05) of ATP in the infarct and ischemic areas, respectively. The nonesterified fatty acid extraction, defined as flow x ([artery] - [GCV]), decreased to 87% +/- 5.6% during occlusion and 75% +/- 20.1% 2 hr after reperfusion, as compared with the control value. CONCLUSION: BMIPP uptake correlated well with lipid metabolism and tissue ATP levels and may prove useful in differentiating myocardial infarction from ischemia in the acute phase of ischemic episodes.

Adenosine Triphosphate↗
PubMed1996

[Basic studies on the 111In labeled antisense oligonucleotide for tumor imaging].

Antisense oligonucleotide labeled with short lived radionuclide has been proposed as a radiopharmaceutical for the detection of abnormal gene expression. In this study, plausibility of 32P or 111In labeled oligonucleotide was basically evaluated using c-erbB-2 protooncogene mRNA as a model target. In cell uptake studies, sequence specific accumulation of 32P-oligonucleotide was found in the cells with c-erbB-2 mRNA expression, but not control cells, indicating the basic possibility of antisense strategy. Synthesis of 111In labeled isothiocyanobenzyl-EDTA (IBE)-oligonucleotide could be performed, but some problems were found in purification step. Stability of 111In-IBE-oligonucleotide was high when compared with that of 32P-oligonucleotide, and in vivo biodistribution data might indicate that 111In-IBE-oligonucleotide was plausible for tumor imaging.

Animals↗
PubMed1996

Metabolic fate of iodine-123-BMIPP in canine myocardium after administration of etomoxir.

UNLABELLED: To clarify the metabolic fate of 123I-(-p-iodophenyl)-3-R,S-methylpentadecanoic acid (BMIPP) in dysfunctional myocardium, a comparison between normal dogs and those with etomoxir administration was studied using an open-chest canine model. METHODS: Using open-chested dogs under anesthesia, we created a system to release all the blood in the great cardiac vein outside without recirculation, if necessary. Iodine-123-BMIPP was directly injected into the left anterior descending artery, its extraction, retention and washout rate in the early phase were calculated, and the metabolites in the myocardium were evaluated using a high-performance liquid chromatography. Moreover, these factors were compared between normal dogs and those pretreated with etomoxir, that creates a condition similar to ischemia. RESULTS: Although rapid extraction of BMIPP from the plasma into the myocardium and the subsequent retention were unchanged, early washout (8 min) of radioactivity significantly increased (49.6% +/- 13.3%-->70.5% +/- 10.7%, p < 0.05) with etomoxir. The levels of the full metabolite formed by complete oxidation of BMIPP decreased significantly with etomoxir (21.4% +/- 10.9%-->5.5% +/- 3.5%, p < 0.01). In addition, back diffusion of BMIPP increased (25.1% +/- 8.0%-->41.9% +/- 12.0%, p < 0.05) in the etomoxir-treated animals without affecting the levels of alpha-oxidation metabolite and the intermediate metabolites. CONCLUSION: BMIPP is very sensitive to etomoxir and is suitable for assessing mitochondrial dysfunction. Iodine-123-BMIPP might be a promising radiopharmaceutical for the evaluation of ischemic heart disease, cardiomyopathy and mitochondrial encephalomyopathy.

Animals↗
PubMed1996

Generator-produced copper-62-PTSM as a myocardial PET perfusion tracer compared with nitrogen-13-ammonia.

UNLABELLED: The purpose of this study was to determine the suitability of 62Cu-pyruvaldehyde bis(N4-methylthiosemicarbazone) (62Cu-PTSM) for estimating myocardial blood flow (MBF) over a wide range of flow by comparison with 13N-ammonia (13NH3). METHODS: PET studies using 62Cu-PTSM and 13NH3 were performed at rest and after pharmacological vasodilatation in 9 normal subjects and 13 patients with coronary artery disease (CAD). According to the microsphere method, values for the product of the extraction fraction and MBF (ExMBF) were calculated using both tracers. In static images, the percent uptake (normalized to the peak count) of each tracer was measured in patients with CAD. RESULTS: The myocardial tracer distribution in the normal subjects was significantly higher in the inferior wall in the 62Cu-PTSM studies and lower in the lateral wall in the 13NH3 studies. The ExMBF values showed linear correlation for both tracers in a low flow range. In a high flow range, however, the ExMBF values for 62Cu-PTSM were nonlinearly proportional to the increase of those for 13NH3 (y = 1.1 x -0.21x2, r = 0.81). The percent uptake for both tracers at baseline well correlated linearly (y = 10.4 + 0.88x, R = 0.91). After pharmacological vasodilatation underestimation of blood flow with 62Cu-PTSM was noted compared to that with 13NH3 at high flows (y = 31.8 + 0.63x, r = 0.76). CONCLUSION: These results suggest that the MBF estimates using 62Cu-PTSM in a low flow range may be as accurate as those with 13NH3. In a high flow range, however, the extraction fraction of 62Cu-PTSM is considered to be lower than that of 13NH3, and this may limit the estimation of MBF with 62Cu-PTSM after pharmacological vasodilatation.

Ammonia↗