Hepatic cytochrome P-450-dependent monooxygenase systems of the trout, frog and snake--I. Components

1. Components of the hepatic monooxygenase systems (cytochrome P-450, cytochrome b5, NADPH cytochrome P-450- or c-reductase) of the brown trout (Salmo trutta), leopard frog (Rana pipiens) and garter snake (Thamnophis) were considerably lower than those found in the rat. 2. Reactivity of snake NADPH-cytochrome P-450-reductase with cytochrome P-450 was about twice that of the rat reductase; reactivities of trout and frog reductases were similar, but lower than that of the rat. The optimal temperature for the rat, frog and snake reductase activity was 37 degrees C, but 26 C for the trout reductase, regardless of whether cytochrome P-450 or cytochrome c was the electron acceptor for the reaction. 3. A type I substrate (benzphetamine) and a type II substrate (aniline) were less reactive with P-450 cytochrome from the trout, frog and snake than with P-450 cytochrome from the rat. 4. Qualitative differences were seen in the ethylisocyanide spectrum of microsomes from the rat, trout, frog and snake; these differences reflect qualitative differences in the populations of P-450 cytochromes among each of the four species.