Determination of nanogram amounts of catecholamine metabolites in amniotic fluid

Assessment of O-methylated catecholamine levels in plasma and urine for diagnosis of autonomic disorders

The term 'metanephrines' is used to indicate the two catechol 3-O-methylated metabolites of epinephrine (E) and norepinephrine (NE): metanephrine and normetanephrine (NMN). The corresponding 3-O-methylated metabolite of dopamine is usually referred to as 3-methoxytyramine rather than 3-methoxydopamine and is not generally considered a "metanephrine". O-Methylation occurs outside the sympathetic neuron and neuroeffector junction. Metanephrines are products of the enzyme catechol-O-methyltransferase (COMT). Subsequent conjugation with sulfate or deamination by monoamine oxidase (MAO) followed by reduction to vanilmandelic acid (VMA) facilitates urinary excretion. For the clinician, measurement of normetanephrine provides an index of norepinephrine released during sympathetic nervous system activity, whereas metanephrine concentration provides an indication of adrenal medullary metabolism of epinephrine prior to its discharge into the circulation. Plasma epinephrine concentration is the preferable index of adrenal medullary epinephrine discharge. Pheochromocytomas, with their protean clinical manifestations, may be diagnostic challenges, but assay of metanephrines, especially plasma metanephrine, can be particularly helpful in diagnosis. These COMT metabolites may also help in elucidation of still undiscovered genetic and acquired disorders of catecholamine metabolism.

Difference in the concentration of tryptophan metabolites between maternal and umbilical foetal blood

Maternal and umbilical foetal blood at delivery were analysed for tryptophan metabolites by using fully automated high-performance liquid chromatography. The metabolites detected in 100 microliters of maternal plasma were kynurenine, serotonin, 5-hydroxyindoleacetic acid, indolelactic acid, indoleacetic acid and indolepropionic acid. These metabolites were present in various amounts in the protein-bound form. Except for indolepropionic acid, the concentrations of tryptophan metabolites were significantly higher in umbilical foetal plasma than in maternal plasma. In addition, 3-hydroxyanthranilic acid was present in umbilical foetal blood, but not in maternal blood. Furthermore, kynurenic acid was also detected in amniotic fluids.

Derivatization reactions in the gas—liquid chromatographic analysis of drugs in biological fluids

Alkylation, acylation, silylation and other derivatization reactions applied to the gas chromatographic analysis of drugs in biological matrices are reviewed. Reaction conditions are discussed in relation to reaction mechanisms. Detector-oriented labelling of drugs, and derivatization with chiral reagents for the separation of enantiomers are surveyed. Data on the sample clean-up, derivatization and GLC analysis of more than 300 drugs and related compounds are listed.