Kveder, Iskric & Keglevic (1962) described the formation of 5-hydroxytryptophol from 5-hydroxytryptamine (5HT) in vivo in rats. The alcohol was isolated as conjugates from urine, and distinguished from 1'-N-acetyl 5-hydroxytryptamine by paper chromatography. Feldstein & Wong (1965) demonstrated the enzymatic conversion of 5HT to 5-hydroxytryptophol in rat liver. The alcohol appears also to be a major metabolite of the amine in platelets (Bartholini, Pletscher & Bruderer, 1964).The isolation of the alcohol from bovine pineal gland by McIsaac, Farrell, Taborsky & Taylor (1965) led us to attempt the synthesis of 5-hydroxytryptophol from 5HT in rat and subsequently human brain homogenates.
METHODS Reagents5-hydroxytryptamine creatinine sulphate was obtained from Koch-Light Ltd., Colnbrook, and 5-hydroxyindolacetic acid from Roche Products, Hertfordshire. The authenticated sample of 5-hydroxytryptophol was a gift from the National Institutes of Health, Bethesda.
Preparation of brain homogenatesWistar strain rats of either sex weighing 180-220 g were used. The animals were killed by decapitation and the brain was quickly taken out. After removal of the cerebral hemispheres and cerebellum the remainder of the brain was homogenized in 25 vol. 0.25M sucrose at 40; 1 ml. of the homogenate was preincubated in a metabolic shaking incubator for 15 min at 370. The reaction was started by the addition of 80 ,ug of 5HT in 1 ml. of 0.5M phosphate buffer, pH 7.4 (Feldstein & Wong, 1965), containing 500 ug of one of the pyridine nucleotide co-enzymes (nicotinamide adenine dinucleotide (NAD), nicotinamide adenine dinucleotide reduced (NADH2), nicotinamide adenine dinucleotide phosphate (NADP) and nicotinamide adenine dinucleotide phosphate reduced (NADPH2)). The reaction was stopped at varying intervals by the addition of 0.1 ml. conc. HCI. Human brain material obtained at necropsy from an adult female was examined in a manner similar to that described above-that is, samples of midbrain and cerebral cortex were dissected, homogenized in 25 vol. 0.25M sucrose at 40 and incubated with 5HT, etc.Estimation of 5-hydroxytryptophol, S-hydroxyindol-3-yl acetaldehyde and S-hydroxyindol-3-yl acetic acid (5HIAA) The analyses were a modification of the method reported by Feldstein & Wong (1965). Duplicate incubation mixtures were pooled and centrifuged at 3,000 rev/min for 7 min. After decantation the pH of the supernatant was adjusted to 7.4 (glass electrode) using SN NaOH, and passed through