@entity1068 -, fasting-, and @entity1324 -inducible cytochromes P-450 in XXXX liver: regulation and characteristics of enzymes belonging to the IIB and IIE gene subfamilies.

@entity4314 @entity535 @entity1324 @entity4921 @entity1110 @entity7935 @entity11920 @entity35 @entity1068
Two major forms of hepatic microsomal cytochrome P-450 were purified from starved and @entity1324 -treated @entity35 . On the basis of @entity535 sequence analysis, they were identified as @entity11920 and @entity4921 . @entity1068 or @entity1324 treatment of @entity35 caused a 9-fold increase in the amount of @entity11920 in liver microsomes accompanied by similar increases in the rate of @entity1110 -dependent metabolism of @entity4314 , @entity1324 , and @entity7935 . Immunological experiments indicated that @entity11920 constitutes the major catalyst of the microsomal metabolism of the latter agents and contributes by about 50% to microsomal P-450-dependent @entity1068 oxidation under the conditions used. The @entity11920 -dependent catalytic activities had a high rate of turnover. In contrast, this was not the case for the immunodetectable @entity11920 , indicating the occurrence of inactive forms of this protein in microsomes. Starvation or @entity1068 or @entity1324 treatment caused 10-30-fold increases in the amount of both mRNA and apoprotein of @entity4921 ,e compared to control. Run-on experiments and the concomitant increases of the @entity4921 gene products at the mRNA and protein levels indicated the appearance of mainly a transcriptional activation by @entity1324 , @entity1068 , or starvation. Fasting exerted, in addition, a pronounced synergistic effect on @entity1324 -dependent induction of @entity4921 ,e mRNA (3-fold), apo- @entity4921 ,e (4.3-fold), @entity11920 mRNA (2-fold), and apo- @entity11920 (2-fold). No increase of mRNA coding for @entity11920 , compared to control, was seen after @entity1324 or @entity1068 treatment alone. The results indicate that effects of @entity1068 , @entity1324 , and/or starvation on drug and xenobiotic metabolism are caused by the induction of P-450 forms belonging to at least two gene subfamilies.
