The hepatic cytochrome level in the cat (Felis catus): normal value and variations in relation to some biological parameters.

1. The average level of the hepatic hydroxylating cytochrome was determined in the cat (0.380 +/- 0.085 nmol.mg-1 proteins). 2. Great individual differences were noted. 3. The level of cytochrome increases with age in the immature (age less than or equal to 8.5 months) and young adults (age: 10-18 months). It is diminished in the older animals. 4. The measured average level is lower than that in other species, and approaches the human one. 5. The induction capacity of phenobarbital is lower in the cat than in other mammals, for example the rat or the mouse.