The effect of riboflavin and mepacrine on the metabolism of 5-hydroxytryptamine

Abstract

The effect of mepacrine and of riboflavin deficiency on 5-hydroxytryptamine metabolism has been studied in vivo and in vitro. In rats dosed with the amine, prior treatment with mepacrine increased excretion of 5-hydroxyindolylacetic acid. Riboflavin deficiency frequently had the same effect. Mepacrine did not affect formation of the acid in the supernatant fraction of homogenized guinea pig liver but it decreased the disappearance of the amine along other pathways. Riboflavin deficiency resulted in decreased disappearance of the amine in supernatants of rat liver but not in the particulate fractions. A hypothesis has been proposed that in mammalian tissue there is a pathway of metabolism of 5-hydroxytryptamine, other than the one catalysed by monoamine oxidase, which is sensitive to flavoenzyme inhibition and to riboflavin deficiency.