Epinephrine 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... 

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

One monoamine oxidase has been found soluble in nature, and has been purified. This is the enzyme of blood serum, which has been purified 200-fold from steer plasma. The specificity of the serum enzyme is more restricted than those of the hver enzymes tryptamine and epinephrine are not oxidized rapidly, if at all, although phenylethylamine is a substrate. The polyamines spermine and spermidine are among the best substrates, and decamethylenediamine, but not shorter diamines, is also attacked. Aromatic substitutions on methylamine form substrates that permit spectrophotometric assays. Benzylamine and furfurylamine, for example, which do not absorb fight in the region used, are converted to benzaldehyde and furfuraldehyde, respectively these products have absorption maxima near 250 mja and 275 m/ . 

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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