Simultaneous analysis of plasma phenethylamine, phenylethanolamine, tyramine and octopamine in patients with hepatic encephalopathy

Patients with hepatic failure often manifest neurological disorders, encephalopathy and cardiovascular abnormalities of hemodynamics such as high cardiac output, low peripheral vascular resistance and renal circulatory failure. Impaired amine metabolism has been proposed to explain the pathogenesis of these symptoms [l-5]. In particular, plasma and brain levels of aromatic trace amines have been reported to be raised in patients with hepatic encephalopathy and in animal models of hepatic disorder [G-12]. These trace amines, including phenethylamine, phenylethanolamine, tyramine and octopamine, are derived from phenylalanine and tyrosine, which are normally metabolized in the liver, and may interfere with neural transmission of noradrenaline and dopamine in the central and peripheral nervous systems [l]. Plasma levels of octopamine were reported to be significantly increased in patients with hepatic encephalopathy [6-lo]. Capocaccia et al. [Ill found that plasma levels of phenylethanolamine correlated with the grade of encephalopathy more than those of octopamine. Faraj et al. [12] reported the etiological significance of h~ertyramine~a observed in patients with hepatic encephalopathy. Besides these amines, attention should be paid to phenethyla~ne, which has been reported to be a neuromodulator [13] and may penetrate through the blood-brain barrier [14]. Since these trace amines undergo similar metabolism and may be interconvertible [15], simultaneous determination of these amines are indispensable to investi-