Hepatic drug metabolizing enzyme activity in the channel catfish, Ictalurus punctatus

1. Several pathways of drug metabolizing enzymic activity were measured in hepatic fractions of the channel catfish and rat using model substrates. The pathways examined included the O-demethylation of p-nitroanisole, microsomal ester hydrolysis of procaine and glucuronidation of p-nitrophenol, and the cytosolic acetylation of sulfamethazine and sulfation of 2-naphthol. Catfish liver preparations were incubated at both 25 degrees C and 37 degrees C. 2. The oxidative metabolism of p-nitrophenol was only one-eighth that of the rat at 37 degrees C and one-twelfth that of the rat at 25 degrees C. 3. Procaine ester hydrolysis was negligible in catfish microsomal preparations. 4. At 37 degrees C, p-nitrophenol glucuronidation was equivalent in catfish and rat microsomes. 5. Catfish cytosolic preparations exhibited N-acetyltransferase and arylsulfotransferase nearly comparable to those of the rat. 6. Rates of glucuronidation and sulfation were higher at 37 degrees C than at 25 degrees C in hepatic fractions of catfish.