A study on the origins of urinary serotonin and tryptamine.

A sensitive gas chromatography/negative ion chemical ionization mass spectrometric (GC/NICIMS) method was devised and by using deuterated L-tryptophan-3,3-d2(Trp-d2) as a tracer, the detailed in vivo metabolism of serotonin (5-HT) and tryptamine (TA) was investigated. A human was administered orally with 10 mg/kg Trp-d2 and rats were injected intra-peritoneally with 50 mg/kg Trp-d2. The ratios of the level of 5-HT-d2 derived from Trp-d2 to that of endogenous 5-HT-d0 and that of TA-d2 to that of TA-d0 were measured in urine and some organs of rats at times up to 4 hr after administration. It is concluded that urinary excretion of 5-HT might reflect its turnover in the central nervous system and that of TA might reflect its peripheral turnover.