%0 Journal Article %A W. LEVIN %A D. RYAN %A S. WEST %A A. Y. H. LU %T n-OCTYLAMINE DIFFERENCE SPECTRA OF CYTOCHROMES P-450 AND P-448 FROM RAT AND MOUSE LIVER: A SPECIES DIFFERENCE %D 1973 %J Drug Metabolism and Disposition %P 602-605 %V 1 %N 3 %X n-Octylamine binds to oxidized liver microsomal cytochrome P-450 to produce a difference spectrum similar to type II binding. This binding spectrum has been used to determine the relative amounts of two forms of cytochrome P-450 in rabbit and mouse microsomes. These two forms of the hemeprotein have been proposed by others to be high- and low-spin cytochrome P-45O, and pretreatment of rabbits and mice with 3-methylcholanthrene results in a change in the ratio of these two forms of the hemeprotein. In contrast to these earlier studies, pretreatment of rats with 3-methylcholanthrene results in no significant change in the ratio of these two forms of the hemeprotein, which indicates a marked species difference. These studies demonstrate that the n-octylamine binding method is not a criterion of induction of the 3-methylcholanthrene-induced hemeprotein in the rat. Copyright © 1973 by The American Society for Pharmacology and Experimental Therapeutics %U https://dmd.aspetjournals.org/content/dmd/1/3/602.full.pdf