Background: Urinary catecholamines and metanephrines have been proposed as a diagnostic tool for identifying canine pheochromocytomas, but the effects of critical illness on urine concentrations of catecholamines and metanephrines is currently unknown. Objectives: To examine the effects of illness on urine concentrations of catecholamines and metanephrines in dogs. Animals: Twenty-five critically ill dogs and twenty-five healthy age- and gender-matched control dogs. Methods: Prospective observational study. Urine was collected from healthy and critically ill dogs and urine concentrations of epinephrine, norepinephrine, metanephrine, and normetanephrine were measured by high-performance liquid chromatography (HPLC) with electrochemical detection. Urinary catecholamine and metanephrine:creatinine ratios were calculated and compared between groups. Results: Urinary epinephrine, norepinephrine, metanephrine, and normetanephrine:creatinine ratios were higher in critically ill dogs when compared to a healthy control population (P = 0.0009, P < 0.0001, P < 0.0001, and P < 0.0001 respectively). Conclusions and Clinical Relevance: Illness has a significant impact on urinary catecholamines and their metabolites in dogs. Further investigation of catecholamine and metanephrine concentrations in dogs with pheochromocytomas is warranted to fully evaluate this test as a diagnostic tool, however the findings of this study suggest that the results may be difficult to interpret in dogs with concurrent illness. / Master of Science

Capillary electrophoretic (CE) separations were successfully coupled to time-of-flight mass spectrometric (TOFMS) detection for the analysis of three families of biological compounds that act as mediators and/or indicators of disease, namely, catecholamines (dopamine, epinephrine, norepinephrine) and their O-methoxylated metabolites (3-methoxytyramine, norepinephrine, and normetanephrine), indolamines (serotonin, tryptophan, and 5-hydroxytryptophan), and angiotensin peptides. While electrophoretic separation techniques provided high separation efficiency, mass spectrometric detection afforded specificity unsurpassed by other types of detectors. Both catecholamines and indolamines are present in body fluids at concentrations that make it possible for them to be determined by capillary zone electrophoresis coupled to TOFMS without employing any preconcentration scheme beyond sample work up by solid phase extraction (SPE). Using this hyphenated approach, submicromolar levels of catecholamines and metanephrines in normal human urine and indolamines in human plasma were detected after the removal of the analytes from their biological matrices and after preconcentration by SPE on mixed mode cation-exchange sorbents. The CE-TOFMS and SPE methods were individualized for each group of compounds. While catecholamines and metanephrines in urine samples were quantitated using 3,4-dihydroxybenzylamine as an internal standard, deuterated isotopes, considered ideal internal standards, were used for the quantitation of indolamines. Because the angiotensin peptides are present in biological fluids at much lower concentrations than the previous two families of analytes, their analysis required the application of additional preconcentration techniques. In this work, the coupling of either of two types of electrophoretic preconcentration methods - field amplified injection (FAI) and isotachophoresis (ITP) - to capillary zone electrophoresis with both UV and MS detection was evaluated. Using FAI-CE-UV, angiotensins were detected at ~1 nM concentrations. Using similar conditions but TOFMS detection, the detection limits were below 10 nM. ITP was evaluated in both single-column and two-column comprehensive arrangements. The detection limits achieved for the ITP-based techniques were approximately one order of magnitude higher than for the FAI-based preconcentration. While the potential usefulness of these techniques was demonstrated using angiotensins standards, substantial additional research would be required to allow these approaches to be applied to plasma as part of clinical assays.

Background: Medication-related interferences with measurements of catecholamines and their metabolites represent important causes of false-positive results during diagnosis of phaeochromocytomas and paragangliomas (PPGLs). Such interferences are less troublesome with measurements by liquid chromatography with tandem mass-spectrometry (LC-MS/MS) than by other methods, but can still present problems for some drugs. Levodopa, the precursor for dopamine used in the treatment of Parkinson’s disease, represents one potentially interfering medication. Methods: Plasma and urine samples, obtained from 20 Parkinsonian patients receiving levodopa, were analysed for concentrations of catecholamines and their O-methylated metabolites by LC-MS/MS. Results were compared with those from a group of 120 age-matched subjects and 18 patients with PPGLs. Results: Plasma and urinary free and deconjugated (freeþconjugated) methoxytyramine, as well as urinary dopamine, showed 22- to 148-fold higher (P<0.0001) concentrations in patients receiving levodopa than in the reference group. In contrast, plasma normetanephrine, urinary noradrenaline and urinary free and deconjugated normetanephrine concentrations were unaffected. Plasma free metanephrine, urinary adrenaline and urinary free and deconjugated metanephrine all showed higher (P<0.05) concentrations in Parkinsonian patients than the reference group, but this was only a problem for adrenaline. Similar to normetanephrine, plasma and urinary metanephrine remained below the 97.5 percentiles of the reference group in almost all Parkinsonian patients. Conclusions: These data establish that although levodopa treatment confounds identification of PPGLs that produce dopamine, the therapy is not a problem for use of LC-MS/MS measurements of plasma and urinary normetanephrine and metanephrine to diagnose more commonly encountered PPGLs that produce noradrenaline or adrenaline.

Background: Measurement of plasma metanephrine, normetanephrine and 3-methoxytyramine is useful in the diagnosis of phaeochromocytomas, but many assays require a large volume of plasma due to poor assay sensitivity, and often require lengthy sample preparation. Our aim was to develop a method for measurement of plasma metanephrines using a small sample volume with minimal hands-on preparation. Methods: Samples were deproteinised using 10 K spin filters prior to online solid phase extraction using a Waters Acquity UPLC Online SPE Manager (Waters, Manchester, UK) coupled to a Waters Xevo TQ-S mass spectrometer (Waters, Manchester, UK). The assay was validated and results compared to a previously published method. Results: We achieved a limit of quantification of 37.5 pmol/L for metanephrine and 3-methoxytyramine and 75 pmol/L for normetanephrine using only 150 mL of sample. The assay was linear up to 30,000 pmol/L for all analytes and in a method comparison study results showed good agreement with a previously published LC-MS/MS assay. Conclusions: We have developed a simple method for measurement of plasma metanephrine, normetanephrine and 3-methoxytyramine using only 150 mL of sample. There is minimal hands-on sample preparation required and the assay is suitable for routine use in a clinical laboratory.