In vivo quantification of renal glucuronide and sulfate conjugation of 1-naphthol and p-nitrophenol in the rat

The simultaneous in vivo renal sulfate and glucuronide conjugations of 1-naphthol (1-N) and p-nitrophenol (PNP) were determined in the rat. In mammals, 1-N and PNP are excreted almost entirely in the urine, mainly as the glucuronide and sulfate conjugates. In male Sprague-Dawley rats, greater than 98% of the infused [14C]1-N (1.0 mumole X min-1 X kg-1) or [14C]PNP (2.0 mumoles X min-1 X kg-1) recovered in urine was identified as the sulfate and glucuronide conjugates. Renal metabolism accounted for a minimum of 20% of the endogenously formed conjugates of either substrate excreted in the urine. The rat kidney formed the glucuronide and sulfate conjugates of PNP at equal rates, whereas the glucuronide: sulfate conjugate ratio for renally formed 1-N conjugates was 3:1. When the conjugates of either 1-N or PNP were infused systemically, in vivo hydrolysis contributed significantly to the amount of circulating parent phenol.