Induction and characterization of cytochromes P450IA and -IIB in the newt, Pleurodeles waltl.

The newt (Pleurodeles waltl) is an amphibian species used in a mutagenicity test (micronucleus). This study was carried out to establish if the inducibility of hepatic cytochromes P450 of this species is similar to that of the rat. Our results showed that the newt is characterized by a lower level of hepatic cytochrome P450-dependent activities than the rat. Variations of enzymatic activities according to sex and season were observed. Specific activities in newt were characterized by an almost complete insensitivity to induction by phenobarbital pretreatment. On the other hand, pretreatment by 3-methylcholanthrene resulted in an increase in the metabolism of several hydroxycoumarin and resorufin derivatives, similar to the effects observed in rat liver. Occurrence of specific forms of cytochromes P450 was assessed by specific antibodies.