Radioenzymatic assay of DOPA (3,4-dihydroxyphenylalanine). [Tritium tracer techniques]

Journal Article · Wed Nov 01 04:00:00 EST 1978 · Clin. Chem.; (United States)

OSTI ID:6340639

Johnson, G A; Gren, J M; Kupiecki, R

We modified the single-isotope radioenzymatic assay for catecholamines (Life Sci. 21, 625(1977)) to assay 3,4-dihydroxyphenylalanine (DOPA). DOPA decarboxylase is used to convert DOPA to dopamine, which concurrently is converted to (/sup 3/H)-3-O-methyldopamine in the presence of catechol-O-methyltransferase and (methyl-/sup 3/H)-S-adenosylmethionine and assayed radioenzymatically. For assay of plasma DOPA, 50 ..mu..l of untreated plasma is added directly into the incubation mixture. A duplicate mixture containing an internal standard requires a second 50-..mu..l aliquot of plasma. Because the assay measures both DOPA and endogenous dopamine, two additional aliquots of plasma must be assayed for dopamine in the absence of the decarboxylase by the differential assay; DOPA is estimated by difference. The assay is sensitive to 25 pg (500 ng/liter of plasma). Analysis of DOPA (DOPA plus dopamine) and the concurrent differential assay of catecholamines in at least 10 samples can be done in a single working day. Plasma DOPA concentrations for 42 normotensive adults were 1430 +- 19 ng/liter (mean +- SEM). In contrast, dopamine concentrations for these same subjects averaged 23 +- 20 ng/liter. Values for the 24 women subjects (1510 +- 62 ng/liter) significantly (P = 0.04) exceeded those for the men (1320 +- 75 ng/liter).

• Research Organization: Upjohn Co., Kalamazoo, MI
• OSTI ID: 6340639
• Journal Information: Clin. Chem.; (United States), Journal Name: Clin. Chem.; (United States) Vol. 24:11; ISSN CLCHA
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
AMINES
AMINO ACIDS
AROMATICS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBOXYLIC ACIDS
CATECHOLAMINES
DOPA
DOPAMINE
DRUGS
ENZYMES
HYDROGEN ISOTOPES
HYDROXY ACIDS
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
PHENOLS
POLYPHENOLS
RADIOASSAY
RADIOISOTOPES
SYMPATHOMIMETICS
TRACER TECHNIQUES
TRITIUM
YEARS LIVING RADIOISOTOPES