Urine analysis norepinephrine

Norepinephrine and epinephrine can be metabolized by several enzymes, as shown in Figure 6-6. Because of the high activity of monoamine oxidase in the mitochondria of the nerve terminal, there is significant turnover of norepinephrine even in the resting terminal. Since the metabolic products are excreted in the urine, an estimate of catecholamine turnover can be obtained from laboratory analysis of total metabolites (sometimes... 

Earlier fluorometric methods for analysis of urinary free catecholamines have been replaced by HPLC methods that allow selective quantitation of epinephrine, norepinephrine, and dopamine. Preliminary extraction of urine is stid required and numerous preanalytical cleanup techniques are available. An alumina extraction procedure is typically coupled with ion-exchange or adsorption chromatography. Alumina pretreatment usually involves a batch extraction technique in which catechols are first adsorbed at pH 8.6 and then eluted with boric acid, which forms a complex with cis-diol groups. Purification on boric acid affinity gels provides an alternative procedure for selective adsorption of catecholamines. 

Vanillylmandehc Acid (VMAj is a major catecholamine metabolite formed by the actions of catechol-0-methyl-transferase and MAO. It is excreted by the kidney and represents an average of 40% to 50% of the urinary excretion production of norepinephrine and epinephrine. Norepinephrine is the major source of VMA, with metabolism through MHPG as the major pathway. VA4A is not significantly conjugated and therefore is measured without a hydrolysis step. VMA was first isolated and identified in the urine of a patient with a pheochromocytoma, and its analysis is commonly performed to detect the presence of pheochromocytomas and neuroblastomas. 

Figure 13.1 Analysis of catecholamines in urine (reproduced with permission of Bioanalytical Systems). Conditions stationary phase, octylsilane mobile phase, citrate-phosphate buffer (pH 4) containing 7% methanol and SOrngl" sodium octyl sulfate electrochemical detector, +700 mV for sample preparation see R.M. Riggin et a ., Anal. Chem., 49, 2109 (1977). Peaks (with concentrations in urine) 1 = norepinephrine (160ngml ) 2 = epinenphrine (31ngml ) 3 = dopamine (202ngmr ) IS —3,4-dihydroxybenzylamine (internal standard).

These diseases are not detected via conventional screening methodology (i.e. organic acids, amino acids etc.), therefore diagnosis relies on the analysis of neurotransmitters and their metabolites in CSF, urine or plasma. In general, TH deficiency leads to low levels of catecholamines and their metabolites, AADC deficiency leads to decreased concentrations of catecholamines, serotonin and their metabolites. In AADC deficiency there is also an accumulation of neurotransmitter precursors, namely 5-hydroxytrypto-phan, levodopa and its methylated derivative, 3-0-methyldopa. D)9H deficiency leads to decreased norepinephrine and an increase in dopamine, and MAO-A deficiency to an increase in the biogenic amines and their 0-methylated catabolites, and to a decrease in concentration of their deami-nated catabolites. 

---