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

Abstract

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°C and 37°C. 2. The oxidative metabolism of p-nitrophenol was only one-eighth that of the rat at 37°C and one-twelfth that of the rat at 25°C. 3. Procaine ester hydrolysis was negligible in catfish microsomal preparations. 4. At 37°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°C than at 25°C in hepatic fractions of catfish.