p-Nitrophenol conjugation in perfused livers from normal and phenobarbital-treated rats: influence of nutritional state.

Conjugation of p-nitrophenol in perfused livers from control and phenobarbital-treated rats was measured spectrally by determining influent minus effluent concentration differences of the free drug. Rates of conjugation (1.0 to 2.0 mu moles/g/h) were essentially the same in livers from fasted control or fasted phenobarbital-treated rats. In control fed livers, rates of conjugation did not differ from the fasted state. However, rates of conjugation in livers from carbohydrate-rich, phenobarbital-treated rats were 6- to 10-fold greater than rates in livers from fasted phenobarbital-treated animals. Differences in rates of conjugation in phenobarbital-treated rats in different nutritional states were more closely related to carbohydrate reserves as indicated by glycogen levels than to activities of p-nitrophenyl UDP-glucuronyl transferase.