AVAILABILITY OF INORGANIC SULFATE AS A RATE LIMITING FACTOR IN THE SULFATE CONJUGATION OR XENOBIOTICS IN THE RAT - SULFATION AND GLUCURONIDATION OF PHENOL

Phenol is converted by the rat in vivo into the sulphate and glucuronide conjugates. When the intravenously administered dose of 14C-labelled phenol was increased from 13 to 266 μmol/kg the percentage glucuronidated increased from 28 to 60 per cent of the dose; the percentage sulphated decreased from 72 to 40 per cent. In rats with intact kidneys the conjugates were almost completely excreted in the urine: when the kidneys were ligated phenylglucuronide was excreted in bile to a high extent, but biliary excretion of phenylsulphate was still very low. Using 35S-labelled sodium sulphate, incorporation of [35S]-sulphate into phenylsulphate could be observed; phenol enhanced the disappearance of [35S]-sulphate from plasma. No significant depletion of inorganic sulphate was found when a high dose of unlabelled phenol (266 μmol/kg) was injected. The literature data on sulphate depletion by substrates of phenolsulphotransferase are critically reviewed; from our data is concluded that the relative decrease of phenol sulphation at high phenol doses is not due to sulphate depletion. © 1979.