Abstract

Tryptamine-¹⁴C was administered to rabbits pretreated with the monoamine oxidase inhibitor pheniprazine. The disposition and metabolism of the radioactive amine was studied. Tryptamine-¹⁴C was found to be present in highest concentration in lung and in lowest concentration in heart and brain. The tissue levels of tryptamine-¹⁴C declined exponentially with a half-life of 35 minutes. Three hours after the administration of tryptamine-¹⁴C, kidney, plasma and duodenum had the highest levels of total radioactivity. In lung, over 50% of the total radioactivity was present as tryptamine. in marked contrast to other tissues examined. Polar basic metabolites were present in highest concentrations in duodenum, kidney and spleen. When reserpine (1 mg/kg i.m.) was administered one hour after tryptamine-¹⁴C, less radioactivity was found in all tissues except kidney and ileum, when compared to control rabbits. Reserpine decreased the tryptamine and polar basic metabolite concentration in several tissues while markedly increaing the levels of polar acidic metabolites in kidney and ileum. 6-Hydroxytryptamine was isolated chromatographically from homogenates of kidney and ileum as well as from urine. The presence of 6-hydroxytryptamine in these biologic materials was increased by enzymatic hydrolysis of its conjugates with sulfatase and β-glucuronidase. In addition, 6-hydroxyindoleacetic acid, the major metabolic product of 6-hydroxytryptamine. was isolated from urine by chromatographic techniques.