Catecholamines determination

The first and still most common LCEC application is determination of the catecholamines in biological samples. The number of papers describing methods for catecholamine determination for certain circumstances are far too numerous to cite, however, several good reviews are available The second major use of LCEC is in the... 

Problems of traceability of total protein and catecholamine determinations in human urine... 

Sorouraddin HM, Hibara A, Kitamori T. Use of a thermal lens microscope in integrated catecholamine determination on a microchip. Fresenius J Chem 2001 371 91-96. 

WHson SP, Kamin DL, Feldman JM. Acetaminophen administration interferes with urinary metanephrine (and catecholamine) determinations. Clin Chem 1985 31 1093-4. 

G.M. Anderson, J.G. Young, PI. Jatlow and D.J. Cohen, Urinary free catecholamines determined by liquid chromatography-fluorometry, Clin. Chem., 27, 2060-2063 (1981). 

Catecholamine determinations of adult adrenal glands have also been made by Hdkfelt and McLean (1950) and by Ozaki (1955). The observations by these investigators are in good agreement with Shepherd and West s values for adult rabbits, whereas considerably higher values were found by Schuler and Heinrich (1949). 

The macrocyclic hexamine [18]aneN6 was further found to recognize catechol, catecholamines and biologically relevant compounds (see Chart II)64). It interacts with all of these donor compounds in neutral pH solutions to form 1 1 complexes, which were determined polarographically. The stability constants pL are summarized in Table 6. 

Although blood pressure control follows Ohm s law and seems to be simple, it underlies a complex circuit of interrelated systems. Hence, numerous physiologic systems that have pleiotropic effects and interact in complex fashion have been found to modulate blood pressure. Because of their number and complexity it is beyond the scope of the current account to cover all mechanisms and feedback circuits involved in blood pressure control. Rather, an overview of the clinically most relevant ones is presented. These systems include the heart, the blood vessels, the extracellular volume, the kidneys, the nervous system, a variety of humoral factors, and molecular events at the cellular level. They are intertwined to maintain adequate tissue perfusion and nutrition. Normal blood pressure control can be related to cardiac output and the total peripheral resistance. The stroke volume and the heart rate determine cardiac output. Each cycle of cardiac contraction propels a bolus of about 70 ml blood into the systemic arterial system. As one example of the interaction of these multiple systems, the stroke volume is dependent in part on intravascular volume regulated by the kidneys as well as on myocardial contractility. The latter is, in turn, a complex function involving sympathetic and parasympathetic control of heart rate intrinsic activity of the cardiac conduction system complex membrane transport and cellular events requiring influx of calcium, which lead to myocardial fibre shortening and relaxation and affects the humoral substances (e.g., catecholamines) in stimulation heart rate and myocardial fibre tension. 

The turnover rate of a transmitter can be calculated from measurement of either the rate at which it is synthesised or the rate at which it is lost from the endogenous store. Transmitter synthesis can be monitored by administering [ H]- or [ " C]-labelled precursors in vivo these are eventually taken up by neurons and converted into radiolabelled product (the transmitter). The rate of accumulation of the radiolabelled transmitter can be used to estimate its synthesis rate. Obviously, the choice of precursor is determined by the rate-limiting step in the synthetic pathway for instance, when measuring catecholamine turnover, tyrosine must be used instead of /-DOPA which bypasses the rate-limiting enzyme, tyrosine hydroxylase. 

Because LCEC had its initial impact in neurochemical analysis, it is not, surprising that many of the early enzyme-linked electrochemical methods are of neurologically important enzymes. Many of the enzymes involved in catecholamine metabolism have been determined by electrochemical means. Phenylalanine hydroxylase activity has been determined by el trochemicaUy monitoring the conversion of tetrahydro-biopterin to dihydrobiopterin Another monooxygenase, tyrosine hydroxylase, has been determined by detecting the DOPA produced by the enzymatic reaction Formation of DOPA has also been monitored electrochemically to determine the activity of L-aromatic amino acid decarboxylase Other enzymes involved in catecholamine metabolism which have been determined electrochemically include dopamine-p-hydroxylase phenylethanolamine-N-methyltransferase and catechol-O-methyltransferase . Electrochemical detection of DOPA has also been used to determine the activity of y-glutamyltranspeptidase The cytochrome P-450 enzyme system has been studied by observing the conversion of benzene to phenol and subsequently to hydroquinone and catechol... 

Felice, L. Felice, J. and Kissinger, P. Determination of catecholamines in rat brain parts by reverse-phase ion-pair liquid chromatography. 

Fenn, R. J., Siggia, S., and Curran, D. J., Liquid chromatography detector based on single and twin electrode thin-layer electrochemistry application to the determination of catecholamines in blood plasma, Anal. Client., 50, 1067,1978. 

The most commonplace substrates in energy-transfer analytical CL methods are aryl oxalates such as to(2,4,6-trichlorophenyl) oxalate (TCPO) and z s(2,4-dinitrophenyl) oxalate (DNPO), which are oxidized with hydrogen peroxide [7, 8], In this process, which is known as the peroxyoxalate-CL (PO-CL) reaction, the fluorophore analyte is a native or derivatized fluorescent organic substance such as a polynuclear aromatic hydrocarbon, dansylamino acid, carboxylic acid, phenothiazine, or catecholamines, for example. The mechanism of the reaction between aryl oxalates and hydrogen peroxide is believed to generate dioxetane-l,2-dione, which may itself decompose to yield an excited-state species. Its interaction with a suitable fluorophore results in energy transfer to the fluorophore, and the subsequent emission can be exploited to develop analytical CL-based determinations. 

The CL enhancement of the lucigenin reaction with catecholamines in the presence of HTAH micelles was used for determination of dopamine, norepinephrine, and epinephrine [42], However, the presence of an anionic surfactant, SDS, inhibits the CL of the system. The aforementioned CL enhancement in the presence of HTAH can be explained in the following way the deprotonated forms of the catecholamines are expected to be the principal species present in aqueous alkaline solution due to the dissociation of the catechol hydroxyl groups, and to react with lucigenin to produce CL. The anionic form of the catecholamines and the hydroxide ion interact electrostatically with and bond to the cationic micelle, to which the lucigenin also bonds. Therefore, the effective concentration of the... 

Neurotransmitter transporters There are probably at least five types of transport protein specific for glutamate, acetylcholine, catecholamines, glycine/GABA and ATP. The type of transporter contributes to determining the transmitter specificity of a synapse. 

G. Alemany, M. Akaarir, A. Gamundi and M.C. Nicolau, Thin-layer chromatographic determinations of catecholamines, 5-hydroxytrypta-mine, and their metabolites in biological samples—a review, J. AOAC Int., 82(1) (1999) 17-24. 

Although some steroids have been reported to reduce the toxic effects of some insecticides, the steroid ethylestrenol decreased the rate of recovery of depressed cholinesterase activity in disulfoton- pretreated rats (Robinson et al. 1978). The exact mechanism of this interaction was not determined. Ethylestrenol alone caused a small decrease in cholinesterase activity, and, therefore, resulted in an additive effect. Rats excreted less adrenaline and more noradrenaline when given simultaneous treatments of atropine and disulfoton compared with rats given disulfoton alone (Brzezinski 1973). The mechanism of action of disulfoton on catecholamine levels may depend on acetylcholine accumulation. In the presence of atropine, the acetylcholine effect on these receptors increases the ability of atropine to liberate catecholamines. 

Chi JD, Odontiadis J, Franklin M. 1999. Simultaneous determination of catecholamines in rat brain tissue by high-performance liquid chromatography. J Chromatogr B 731 361... 

Raggi MA, Sabbioni C, Casamenti G, Gerra G, Calonghi N, et al. 1999. Determination of catecholamines in human plasma by high-performance liquid chromatography with electrochemical detection. J Chrom B 730 201-211. 

Vaarman A, Kask A, Maeorg U. 2002. Novel and sensitive high-performance liquid chromatographic methods based on electrochemical coulometric assay detection for simultaneous determination of catecholamines, kynure-nine and indole derivatives of tryptophan. J Chrom B 769 145-153. 

Peterson ZD, Collins DC, BowerbankCR, Lee ML, Graves SW. 2002. Determination of catecholamines and metanephrines in urine by capillary electrophoresis-electrospray ioniza-tion-time-of-flight mass spectrometry. J Chromatogr B Analyt Technol Biomed Life Sci 776 221. 

Approximately 30 years ago, Schildkraut postulated that noradrenaline may play a pivotal role in the aetiology of depression. Evidence in favour of this hypothesis was provided by the observation that the antihypertensive drug reserpine, which depletes both the central and peripheral vesicular stores of catecholamines such as noradrenaline, is likely to precipitate depression in patients in remission. The experimental drug alpha-methyl-paratyrosine that blocks the synthesis of noradrenaline by inhibiting the rate-limiting enzyme tyrosine hydroxylase was also shown to precipitate depression in patients during remission. While such findings are only indirect indicators that noradrenaline plays an important role in human behaviour, and may be defective in depression, more direct evidence is needed to substantiate the hypothesis. The most obvious approach would be to determine the concentration of noradrenaline and/or its major central... 

Hypertension infrequently results from another disease, such as a catecholamine-secreting tumor (pheochro-mocytoma) in most cases the cause carmot be determined essential (primary) hypertension. Antihypertensive drugs are indicated when blood pressure cannot be sufficiently controlled by means of weight reduction or a low-salt diet. In principle, lowering of either cardiac output or peripheral resistance may decrease blood pressure (cf p. 306,... 

---