The metabolism of dipotassium 2-hydroxy-5-nitrophenyl [35S]sulphate, a substrate for lysosomal arylsulphatases A and B

Abstract

The metabolic fate of dipotassium 2-hydroxy-5-nitrophenyl [35S]sulphate ([35S]NCS), a chromogenic substrate for lysosomal arylsulphatases A and B, has been studied in rats. Intraperitoneal injection of [35S]NCS into free-ranging animals is followed by excretion of the bulk of the radioactivity in the urine within 24hr., less than 13% being eliminated as inorganic [35S]sulphate. Most of the urinary radioactivity can be accounted for as [35S]NCS, but small amounts of a labelled metabolite are also present. Experiments in which [35S]NCS was injected intravenously into anaesthetized rats with bile-duct and bladder cannulae confirm that the ester is rapidly excreted in the urine. However, small amounts of radioactivity appear in bile, mainly in the form of the metabolite detected in urine. When [35S]NCS is perfused through the isolated rat liver, about 35% of the dose is hydrolysed within 3hr. Similar results are obtained if [35S]NCS is injected into anaesthetized rats in which kidney function has been eliminated by ligature of the renal pedicles. The labelled metabolite has been isolated from bile obtained by perfusing several rat livers with blood containing a total of 100mg. of [35S]NCS. It has been identified as 2-β-glucuronosido-5-nitrophenyl [35S]sulphate. The implications of the various findings are discussed. The Appendix describes the preparation of [35S]NCS.