Norepinephrine plasma assays

The use of HPLC to analyze biogenic amines and their acid metabolites is well documented. HPLC assays for classical biogenic amines such as norepinephrine (NE), epinephrine (E), dopamine (DA), and 5-hydroxytryptamine (5-HT, serotonin) and their acid metabolites are based on several physicochemical properties that include a catechol moiety (aryl 1,2-dihydroxy), basicity, easily oxidized nature, and/or native fluorescence characteristics (Anderson, 1985). Based on these characteristics, various types of detector systems can be employed to assay low concentrations of these analytes in various matrices such as plasma, urine, cerebrospinal fluid (CSE), tissue, and dialysate. 

Highly sensitive, specific, and reliable assay methods are required for measuring the normally very low concentrations of epinephrine, norepinephrine, and dopamine in plasma. Both unconjugated (free) and sulfoconjugated catecholamines circulate in human plasma and are increased in plasma from patients with pheochromocytomas. Clinical... 

Anne et al. (2005) demonstrate that a pseudotripeptide inhibitor and its disulfide-coupled dimer could prevent BoNT/B-mediated inhibition of norepinephrine release from cortical synaptosomes. This action was observed in the presence of inhibitor concentrations >15 pM. The relatively high concentrations required for inhibition of BoNT/B on norepinephrine release contrasts with the 2 nM IC50 observed for inhibition of the BoNT/B LC-mediated cleavage of a synaptobrevin peptide in a cell-free enzymatic assay (Anne et al., 2005). The lower potency in cell-based assays appears to reflect the difficulty of these charged peptidomimetic inhibitors to cross plasma membranes, which represents a major limitation of this class of compounds. 

Benjonothan, N. and Porter, J. C., A sensitive radioenzymatic assay for dopamine, norepinephrine and epinephrine in plasma and tissue. Endocrinology, 98, 1497-1507, 1976. 

Among 24 compounds containing the tetrazole function prepared by Holland and Pereira [70], 5-(3-pyridyl)-tetrazole (XIII) was found to depress plasma-free fatty acid levels in the fasted dog most effectively. The hypoHpidemic activity of XIII was comparable to that of nicptinic and 3-pyridyl-acetic acids. In fact, the duration of activity was approximately 5 hours which is three times longer than that of nicotinic acid. Moreover, no rebound effect was observed after the hypoHpidemic activity of XIII, while the short inhibitory action of nicotinic acid was followed by a rise of plasma-free fatty acid concentration above the control level in the fasted dog. In contrast, compound XIII was found to be about 3,000 times less potent than nicotinic acid in the in vitro test in which the inhibition of norepinephrine-induced free fatty acid release from isolated adipose tissue was measured. In this assay, 3-pyridyl-acetic acid (IV) was approximately 600 times less active than nicotinic acid. PicoHnic acid and isonicotinic acid were even less active. The metaboHtes of nicotinic acid in man, namely, nicotinic acid amide, iV -methylnicotinamide and nicotinuric acid, were found to be about 10,000 times less active as Hpolysis inhibitors than nicotinic acid. Based on these findings, 5-(3-pyridyl)-tetrazole... 

An Improved Method for Determination of Plasma Norepinephrine Isolation by Boric Acid Gel and Assay by Selected Ion Monitoring Biomed. Mass Spetrom. 7(9) 396-398 (1980) CA 94 170437f... 

Female rats kept under controlled environmental conditions were given a single intraperitoneal injection of saline solutions of isoproterenol (80 pg), epinephrine (80 or I60 pg), norepinephrine (80 or 160 p.g), dopamine (l mg), vasopressin (500 mU), histamine (300 jig), or 0.9 normal saline (0.2 ml). Throughout this paper all doses are expressed as weight units of free base. Ten minutes after the injection they were decapitated and the plasma separated ffom the pooled heparinized blood, was frozen and stored at -12 C until assayed for its ACTH content. The results as shown in Table 1, indicate that norepinephrine is more potent than epinephrine which is in turn more potent than isoproterenol in stimulating ACTH secretion, and that dopamine, histamine, and vasopressin in larger amounts have a similar effect. Since the potency of the catecholamines in this respect appeared to be... 

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