The Conjugation of 1- and 2-Naphthols and other Phenols in the Cat and Pig

[1-¹⁴C]-Naphthol and [8-¹⁴C]2-naphthol (25 mg/kg) injected into cats were excreted in the urine almost entirely as sulphate conjugates. Only about 1–2% of the dose appeared as naphthylglucuronides. 1-Naphthol gave entirely 1-naphthylsulphate whereas 2-naphthol gave 2-naphthylsulphate and an unidentified hydroxynaphthylsulphate in the ratio of 4 : 1.

When [8-¹⁴C]2-naphthol was injected into pigs (dose 25 mg/kg) it was excreted mainly as 2-naphthylglucuronide with a small amount of 2-naphthyl sulphate (ratio about 15 : 1), but when [1-¹⁴C]1-naphthol was injected, 1-naphthylglucuronide and 1-naphthylsulphate were excreted in the ratio of 2 : 1. The pig, therefore, formed substantial amounts of 1-naphthylsulphate but not of 2-naphthylsulphate.

The cat excreted injected [¹⁴C]morphine mainly as morphine 3-sulphate and [¹⁴C]phenacetin as 4-acetamidophenylsulphate, but injected [³H]phenolphthalein was excreted as the glucuronide and sulphate in the ratio of 3 : 2. The cat, therefore, formed substantial amounts of phenolphthalein glucuronide, but not of morphine 3-glucuronide or 4-acetamidophenylglucuronide.

The pig excreted [¹⁴C]phenacetin mainly as 4-acetamidophenylglucuronide, with small amounts of the corresponding sulphate. About half of injected 4-hydroxy[¹⁴C]amphetamine was excreted unchanged by the pig, the rest being conjugated mainly with glucuronic acid.

The cat tends to excrete phenols mainly as sulphates and the pig mainly as glucuronides, but certain phenols, such as phenolphthalein, form substantial amounts of glucuronides in cats and certain others, such as 1-naphthol, form substantial amounts of sulphates in pigs.