Para-nitropbenol glucuronidation and sulfation in rat and human liver slices

Para-nitrophenol (PNP) is a well-known substrate for both phase I (hydroxyl ation at cytochrome P450) and phase II reactions (glucuronidation and sulfa tion). HPLC separation of PNP conjugates has already been described, but no t for respective studies with liver slices, which nowadays have proven to b e a suitable model for metabolic studies. Therefore we adapted an HPLC meth od for the simultaneous measurement of PNP glucuronidation (PNP-G) and sulf ation (PNP-S) in this in vitro system. Both activities are substantially ma intained over an incubation period of 24 h. PNP-G activity, however, seems to be better preserved, as indicated by stable values for PNP-G but reduced PNP-S values after 48 h liver slice prc incubation. 24 h exposure of the s lices to beta-naphthoflavone or phenobarbital does not change PNP-G or PNP- S activities.