Disease relevance of ammonia

• METHODS AND RESULTS: PET with [13N]ammonia measured myocardial blood flow and flow reserve in 15 patients with symptomatic chronic ischemic heart disease [1].
• Ischemia was defined as a significant reduction (> 2 SDs from average counts/pixel in maximally perfused zones) in [13N]ammonia retention within 10 contiguous myocardial sectors coupled with an increase or no change in counts derived from [18F]fluorodeoxyglucose [2].
• Positron emission tomography with appropriate tracer kinetic models using [13N]ammonia and [15O]water provides an accurate quantitative method for measuring regional myocardial blood flow over a wide range of flow values in normally contracting or akinetic canine myocardium in the absence and in the presence of infarction [3].
• METHODS AND RESULTS: Myocardial blood flow at rest and after dipyridamole-induced hyperemia (0.56 mg/kg i.v.) was quantified with [13N]ammonia and positron emission tomography in 13 volunteers before and upon completion of a 6-week program of cardiovascular conditioning and a low-fat diet [4].
• Viable myocardium had both flow > 0.45 ml/min per g and VD > 2.0 ml/g. Nitrogen-13 ammonia kinetic modeling permits determination of blood flow and metabolic integrity in patients with previous myocardial infarction and can help differentiate between scar and ischemic but viable myocardium [5].

High impact information on ammonia

• Positron emission tomography (PET) can be used with nitrogen-13-ammonia (13NH3) to estimate regional myocardial blood flow, and with fluorine-18-deoxyglucose (18FDG) to measure exogenous glucose uptake by the myocardium [6].
• Intratracheal administration to mice of radioactive nitrite labeled with nitrogen-13 (13NO2-) (half-life, 9.96 minutes) in dosages that do not cause pharmacological perturbation reveals that oxidative and reductive reactions occur in different organs [7].
• Nitrogen-13 from both anions was distributed uniformly between plasma and blood cells [8].
• METHODS AND RESULTS--Thirty-seven patients (mean age, 59 +/- 11 years) with coronary artery disease and impaired left ventricular function (ejection fraction, 34 +/- 10%) were studied with PET using FDG and [13N]ammonia before surgical coronary revascularization (3 +/- 1 grafts per patient) [9].
• Following a bolus injection of tracer quantities of [13N]ammonia into the portal vein, the single pass extraction was approximately 93%, in good agreement with the portal-hepatic vein difference of approximately 90% [10].

Chemical compound and disease context of ammonia

• METHODS AND RESULTS: Measurements of myocardial blood flow were made with PET [13N]ammonia in 12 patients with ischemic heart disease (11 men; age, 65+/-8 years [mean+/-SD]) at rest and during adenosine at 70 and then 140 microg . kg-1 . min-1 for 5 minutes each before and approximately 4 months after simvastatin treatment (40 mg daily) [11].
• This study was designed to test the usefulness of nitrogen-13 (N-13) glutamate imaging with positron emission tomography in defining myocardial ischemia in humans [12].
• To assess metabolic activity in segments with persistent defect, stress TI-201 tomography and positron emission tomography using nitrogen-13 ammonia and fluorine-18 2-fluoro-deoxyglucose (FDG) were performed in 28 patients with healed myocardial infarction [13].
• Quantitative scanning of soft-tissue sarcomas with nitrogen-13-labeled L-glutamate [14].

Biological context of ammonia

• This study tested the hypothesis that nonviable myocardium can be identified by quantitative measurements of regional myocardial blood flow obtained using positron emission tomography in conjunction with a mathematical model of nitrogen-13 (N-13) ammonia tracer kinetics [15].
• Coronary vasodilation is impaired in both hypertrophied and nonhypertrophied myocardium of patients with hypertrophic cardiomyopathy: a study with nitrogen-13 ammonia and positron emission tomography [16].
• Quantitative evaluation of regional pulmonary ventilation using PET and nitrogen-13 gas [17].
• Myocardial oxygen consumption was invasively determined by the Fick method from arterial and coronary sinus O2 concentrations and from MBF obtained by [13N]ammonia PET [18].
• The present findings emphasize the importance of the lungs in the maintenance of whole-body nitrogen homeostasis and suggest the use of [13N]ammonia and 13N-labeled amino acids as non-invasive probes in the study of normal and diseased lung metabolism [19].

Anatomical context of ammonia

• The amount of label recovered in the right cerebral hemisphere, 5 s after a rapid bolus injection of [13N]ammonia via the right common carotid artery, was found to be independent of ammonia concentration within the bolus over a 1000-fold range [20].
• After infusion of physiological concentrations of [13N]ammonia for 10 min via one internal carotid artery, the relative specific activities of glutamate, glutamine (alpha-amino), and glutamine (amide) in brain were approximately 1:5:400, respectively [20].
• Conventional cardiac PET modeling techniques for [13N]ammonia flow determination do not fully account for the effects of spillover of activity from the right ventricle (RV) onto the activity in the myocardial septum [21].
• PET tomographic imaging of the human heart, pancreas, and liver with nitrogen-13 derived from [13N]-L-glutamate [22].
• Bolus injection of [13N]ammonia into the femoral vein of pentobarbital-anesthetized rats was followed by rapid clearance from the blood and first-pass extraction of nearly 30% by the lungs [19].

Associations of ammonia with other chemical compounds

• Dynamic positron tomographic imaging with nitrogen-13 glutamate in patients with coronary artery disease: comparison with nitrogen-13 ammonia and fluorine-18 fluorodeoxyglucose imaging [12].
• Dual-isotope SPECT may provide an alternative, accurate, cost-effective method to nitrogen-13 ammonia/F-18 fluorodeoxyglucose positron emission tomography or thallium-201 reinjection for identifying injured or dysfunctional but viable myocardium [23].
• OBJECTIVES: We sought to prospectively compare nitrogen-13 (13N)-ammonia/18fluorodeoxyglucose (18FDG) positron emission tomography (PET)-guided management with stress/rest technetium-99m (99mTc)-sestamibi single-photon emission computed tomography (SPECT)-guided management [24].
• Myocardial blood flow (MBF) during dipyridamole (DP) loading and baseline MBF were measured by using positron emission tomography and [13N]ammonia, after which MVD was calculated [25].
• Quantitative scanning of osteogenic sarcoma with nitrogen-13-labeled L-glutamate [26].

Gene context of ammonia

• Dynamic PET using [13N]ammonia was performed in patients with primary hepatocellular carcinoma (hepatoma) [27].
• Activity of glutamine synthetase was coupled to activity of nitrogenase in isolated heterocysts as shown by acetylene-inhibitable formation of [13N]NH3 and of amidelabeled [13N]glutamine form [13N]N2 [28].
• Furthermore, we studied MBF as assessed by [13N]ammonia in 15 IDDM patients without coronary artery disease [29].
• [13N]Ammonia and L-[amide-13N]glutamine metabolism in glutaminase-sensitive and glutaminase-resistant murine tumors [30].
• Separation and further purification of ammonia were performed with GC, leading to 5s pulses (1.1 ml STP) with 3.5 +/- 0.5 MBq [13N]NH3 with a high chemical and radiochemical purity suited for positron emission profiling (PEP) [31].

Analytical, diagnostic and therapeutic context of ammonia

• METHODS AND RESULTS: Myocardial perfusion with [13N]ammonia was estimated from dynamic time-activity curves at baseline and 3 hours following application of either a 0.4 mg/h GTN skin patch (n = 10) or a placebo patch (n = 10) in a double-blind parallel design [2].
• In large regions of interest (5 cm3), a good correlation between the microsphere method and [13N]ammonia (with metabolite correction) was obtained (y = 3 + 0.78x, r = 0.94) [3].
• Noninvasive evaluation of regional myocardial perfusion in 112 patients using a mobile scintillation camera and intravenous nitrogen-13 labeled ammonia [32].
• OBJECTIVES: Regional myocardial blood flow (MBF) and flow reserve measurements using nitrogen-13 (N-13) ammonia positron emission tomography (PET) were compared with quantitative coronary angiography to determine their utility in the detection of significant coronary artery disease (CAD) [33].
• METHODS: PET studies of myocardial sympathetic innervation, myocardial perfusion and oxygen utilization using [11C]hydroxyephedrine (HED), [13N]ammonia and 1-[11C]acetate, respectively, were performed before and approximately 2 and 8 wk after surgical left thoracotomy and regional chemical sympathetic denervation (n = 5) [34].

References