Endogenous sulphate acceptors in rat liver

Abstract

In the presence of adenosine triphosphate, Mg2+ and SO4 2- ions particle-free supernatants of iso-osmotic-potassium chloride homogenates of rat liver accumulated adenosine-3[image]-phosphate 5[image]-sulphatophosphate. The rate of accumulation of adenosine-3[image]-phosphate 5[image]-sulphatophosphate depended both on the rate of synthesis and the rate of breakdown. In the absence of adenosine triphosphate the rat-liver preparation degraded adenosine-3[image]-phosphate 5[image]-sulphatophosphate to SO4 2- ions and adenosine monophosphate and eventually adenosine. One mechanism of degradation involved 3[image]-dephos-phorylation to give adenosine-5[image]-sulphatophosphate, which was then desulphated yielding SO4 2-ions and adenosine monophosphate. Both stages of this reaction were inhibited by ethylenediaminetetra-acetic acid. A further fate of the sulphate group of adenosine 3[image]-phosphate 5[image]-sulphatophosphate in the presence of the liver extract was to be transferred to endogenous acceptors with the formation of sulphate esters. Extracts of kidney, spleen, heart, lung and testes produced adenosine 3[image]-phosphate 5[image]-sulphatophosphate and transferred sulphate from this compound to endogenous acceptors. Evidence has been obtained which suggests that some of the endogenous acceptors are phenols and possibly steroids. The radiochromatograph patterns of urine and bile from rats which had received injections of Na235SO4 were compared with the radiochromatographs of the sulphated endogenous acceptors of liver. Some common radioactive spots were observed. On incubation of various potential sulphate acceptors with the liver extract in the presence of adenosine triphosphate, Mg2+ and 35SO42-ions new radioactive spots were observed on chromatograms. Evidence suggesting that these spots were the sulphate esters of the acceptors has been presented but pitfalls in the interpretation of the chromatograms have been pointed out. In this system sulphate esters were formed from all the tested phenols, steroids, alcohols and arylamines. Tyramine, adrenaline and propane-1, 2-diol each gave 3 new radioactive spots. Bilirubin, cholic acid, L-threonine, L-serine, L-hydroxyproline; L-hydroxyglutamic acid and choline chloride did not appear to be sulphated.