Dose-dependent intestinal and hepatic glucuronidation and sulfatation of P-nitrophenol in the rat

The jejunum was able to metabolize p-nitrophenol (PNP) rapidly and to transport the metabolites efficiently back into the luminal solution. About 21, 16, 6 and 3.5% of recirculated amount of PNP could be detected in 90 minutes as glucuronide in the lumen of jejunal loop, when 20, 100, 500 or 1,000 microM PNP was perfused, which shows that the luminal appearance of p-nitrophenol-glucuronide (PNP-G) tended to saturability. Biliary excretion rate of PNP-G was lower than the luminal appearance of this metabolite, when PNP was recirculated at 20 or 100 microM concentrations, however, at higher concentrations (500, 1,000 microM) the biliary excretion exceeded the luminal appearance of this conjugate and no saturability was observed in the biliary glucuronidation of PNP. Biliary excretion of sulfate conjugate of p-nitrophenol (PNP-S) exceeded the luminal appearance of this metabolite.