Preliminary investigations of the metabolism and pharmacological activity of beta-hydroxytryptamines in mammals.

beta-Hydroxytryptamine and beta-hydroxy-5-hydroxytryptamine were incubated with rat liver slices and oxidative deamination was established as the main route of metabolism: in both instances the corresponding indole-3-glycollic acids and indole-3-ethane diols were the major metabolites. However, the rates of deamination of beta-hydroxylated tryptamines, as measured manometrically, were found to be much slower than those of tryptamines nonhydroxylated in the side chain. The pharmacological activities of beta-hydroxylated tryptamines were tested in guinea-pigs on resistance of respiratory pathways, spontaneous respiration, electrocardiogram, blood pressure and isolated ileum, using tryptamine and 5-HT as reference substances. The effects of tryptamines hydroxylated in the side chain were in general similar to those of corresponding tryptamines but of much lower intensities; only in increasing the blood pressure was beta-hydroxytryptamine as active as tryptamine. The different reactions of these two groups of substances in the presence of some antagonists indicate that the receptors are probably not the same.