The turnover rates of phenylethylamine and tryptamine have been estimated as their rates of accumulation after inhibition of monoamine oxidase by pargyline and were found to be 1.53 nmoVgih and 0.24 nmoligih, respectively. Rate constants for the substrate activities of these amines towards monoamine oxidase were calculated as 100 h-* and 150 h-l, respectively. Tryptamine was found to exhibit a biphasic response to increasing pargyline dosage, demonstrating its dual activity to type B and type A monoamine oxidase, for which two rate constants were obtained, kR = 100 h-' and kA = 50 h-l. Address reprint requests to D. A. Durden. Abbreviation used: MAO. Monoamine oxidase. 150 0.28 63d 0.66" 0.54 77 0.83 50 " Data from this paper. The endogenous value was taken from previous work in this laboratory [Philips, un-Warsh et al. (1979); tryptamine concentration was measured after i.p. administration of '' Rate constant and half-life were calculated using the synthesis rate of Warsh et al. (1979)Calculated from the data in Table 2 of Beck et al. (1977); 5-hydroxytryptamine was ' Taken from Fig. 3 of Tozer et al. (1966); 5-hydroxytryptamine concentration was mea-published data, cited by Boulton (197611. 75 mg/kg pargyline. and the endogenous concentration of Philips [unpublished, cited by Boulton (197611. measured 2 h after 100 mg/kg pargyline. sured after i.p. administration of 75 mgkg pargyline.

1974) Identification and Distributionof Tryptamine in the Rat. Can. J. Bbochem. 52,[447][448][449][450][451] A procedure for the quantitative measurement of tryptamine in mammalian tissues is described. The amine is isolated by ion-exchange chromatography, converted to its dansyl derivative, further purified by thin-layer chromatography, and quantitated by the massspectrometric integrated ion current technique using an isotopically labelled internal standard.The concentrations of tryptamine in some tissues of male Wistar rats were (ng/g 9 S.D. ) : brain 0.50 2 0.07, heart 0.62 k 0.10, kidney 8.04 f 2.10, liver 0.73 & 0.07, lung 0.54 k 0.18, and spleen 0.43 f 8.14. In the brain, the hypothalamaas contained 0.94 k 0.22, the cerebellum 0.27 k 0.02, the stem 0.24 2 0.06, the caudate nucleus 2.93 t 1.14, and the "rest" 0.32 2 0.05 ng/g (mean 2 mean deviation). Philips, S. R., Durden, D. A. & Boaalton, A. A. (1974) Identification and Distribution of Tryptamine in the Rat. Can. P. Blsclrem. 52,447-451 Nsus dCcrivons une technique de mesure quantitative de la tryptamine dans les tissus des mammifkres. L'amine est d'abord isolCe par chromatographie Cchangeuse d'ions, transformke en sen dCrivC dansylC, purifike par chromatographie en ceuche mince et mesurCe par la technique Be spectromCtrie de masse infkgrCe h un courant ionique utilisant un standard interne mar& d'un isotope. La concentration de tryptamine dans quelques tissus du rat mgle Wistar est (ng/g k dCviation standard) : cerveau 0.50 k 0.07. coeur 0.62 ? 0.10, rein 8.04 f 2.10, fsie 0.73 2 0.07, poumon 0.54 2 0.18 et rate 0.43 2 0.84. Dans le ceweau, I'hypothalamus contient 0.94 2 0.22, le cemelet 0.27 rk 0.02, B a tige 0.24 + 0.06, le noyau caudC 2.93 t 1.14 et le "reste" 0.32 2 0.05 ng/g (moyenne 2 deviation de la moyenne).[Traduit par le journal]

In 2015 the English Newborn Screening programme expanded to include Isovaleric Acidaemia (IVA). Screening is performed by flow injection analysis tandem mass spectrometry of isovalerylcarnitine. Isovalerylcarnitine is isobaric with pivaloylcarnitine which can be present in blood due to the use of pivalic ester pro-drugs or pivalic acid derivatives used as emollients in some nipple creams; the potential for false positives (FP) is well documented. A pilot study in England screened 438,164 babies, 18 had presumptive positive results but only 4 were confirmed as true positives (TP). We developed a simple test to separate the isobaric compounds and investigate these samples further.We studied newborn screening blood spots from 122 randomised controls and 34 infants with an initial raised C5 result. Dried blood spots were eluted with 30% acetonitrile (150 μL) and injected into a Waters Acquity UPLC coupled to a Waters Premier XE tandem mass spectrometer operating in positive ion mode. Isocratic separation of isovalerylcarnitine, pivaloylcarnitine, valerylcarnitine and 2-methylbutyrylcarnitine was achieved within 8 min. Assay performance characteristics were acceptable and non-parametric reference ranges (n = 122) were determined for each analyte.If this method had been used as a second tier test for the 34 presumptive positive samples, the number of FP's would have reduced from 24 to 8 and the positive predictive value of the screening test would have increased from 29 to 56%. Introduction of this test into the screening protocol has the potential to significantly reduce FP results for IVA and prevent unnecessary anxiety.

beta-Phenylethylamine (PE) hydrochloride injected intraperitoneally into rats was distributed evenly throughout the various regions of rat brain. Similarly, when a mixture of PE and alpha, alpha, beta, beta-deuterated PE [( 2H4]PE) was injected, no regional differences were observed in the ratios of the amounts of [2H4]PE and PE present; however, significantly more [2H4]PE than PE was present, although a 1:1 mixture had been administered. Further experiments in which the amounts of [2H4]PE and PE in whole rat brain, liver, and plasma were quantified confirmed this finding. The maximum [2H4]PE-to-PE ratios observed were 67 in whole brain 1 h after injection and 8 in liver and in plasma 45 min after injection. The whole brain [2H4]PE-to-PE ratios were decreased by pargyline pretreatment. Subsequent experiments showed that more alpha, alpha-[2H2]PE than PE was present in whole brain, liver, and plasma of rats injected with an equimolar mixture of alpha, alpha-[2H2]PE and PE. In contrast, beta, beta-[2H2]PE was not enriched in comparison to PE under the same experimental conditions. We concluded that the basis for the enrichment of [2H4]PE and alpha, alpha-[2H2]PE compared to PE was due to protection of the deuterated analogs from the actions of monoamine oxidase and perhaps aldehyde dehydrogenase; this protection led to pronounced deuterium substitution effects in vivo especially in the brain.