[Biotransformation in hen's eggs. Metabolic transformation of p-nitrophenol]

Not only phase I reactions but also phase II reactions can be detected using embryonated chicken eggs as an alternative method for biotransformation studies. Previously reported investigations which enabled the detection of the phase II products of 7-ethoxycoumarin in the allantois after enzymatic conjugate cleavage have since been supplemented by the development of a direct method. The glucuronidation and sulfation of p-nitrophenol were chosen as model reactions for this direct detection of conjugation reactions. The utility of the previously developed method for application to biotransformation investigations involving the detection of metabolites in the allantois in fertile chicken eggs has now been substantiated for the model substance p-nitrophenol. p-Nitrophenyl sulfate and p-nitrophenyl glucuronide were directly identified as phase II metabolites after incubation and work-up by HPLC analysis as well as comparison of their spectra with those of authentic substances. The conversion rates obtained are very high and well comparable with those of in vivo investigations in chickens. It would seem that the metabolism of hydrophilic substances can be advantageously studied in chicken eggs.