Metabolism and biliary excretion of arylaminosulphonic acids in the rat

Abstract

Introduction Comparatively little work has been published on the metabolism of arylaminosulphonic acids in any animal species. The metabolism of these compounds is of interest because several of them occur as metabolic products after the ingestion of azo food colourings. One of the simplest compounds in the series, sulphanilic acid, gives N-acetylsulphanilic acid as the sole metabolite after administration to a number of species (McMahon & O'Reilly, 1969). It seems likely that the amine group in acids of this type would be acetylated to some extent, but their metabolism does not appear to have been studied previously (Williams, 1959). Some aminophenoland other aromatic sulphonic acids have been reported to be excreted unchanged (Young & Maw, 1958; Sammons, Shelswell & Williams, 1941). The only reported work on the biliary excretion of these compounds was by Abou-elMakarem, Millburn, Smith & Williams (1967), who studied sulphanilic, metanilic and orthanilic acids in the rat and found only negligible biliary excretion of the acids and no metabolites in the bile. Williams, Millburn & Smith (1965) have postulated that, among other requirements, a relatively high molecular weight (above 300) is essential for a compound that is to be excreted in the bile. The study described here was undertaken on the grounds that the series of compounds available, especially if conjugated in the liver, might allow better definition of the structural requirements for biliary excretion.