Studies on the Mechanism of Biliary Excretion of Aryl Sulphates in the Rat

The present investigation was therefore extended to examine the effects of p-benzoquinone and 2,6-dimethoxybenzoquinone on cat liver mitochondria (Chappell & Hansford, 1972). It was shown that both quinones are potent inhibitors of mitochondria1 respiration. Mitochondria could be protected by an equimolar concentration of cysteine. A predictable consequence of the presence of quinones is the formation of elevated amounts of methaemoglobin, and this prediction was verified : the value of methaenioglobin reached 12% in cats l h after administration of [U-14C]phenol (20mg/kg body wt.). Similar values were recorded with 2,6-dimetho~y[U-'~C]phenol and [2,3,5,6J4C]quinol. In many other species, e.g. the rat, phenols are readily detoxicated by forming glucuronic acid conjugates (Dutton, 1966). However, it is known that cats do not readily form glucuronides (Robinson & Williams, 1958), and the present study shows that sulphate conjugation is a major detoxication mechanism. Further, this mechanism is apparently saturated readily and the toxic effects of phenols are explicable in terms of the oxidation products of unconjugated phenols.