Biochemical effects of dietary intakes of different broccoli samples. I. Differential modulation of cytochrome P-450 activities in rat liver, kidney,and colon

Modulation of xenobiotic metabolism, including cytochrome P-450 (CYP) enzym e activities, due to dietary intakes of cruciferous vegetables, has been de scribed in animals and humans, and the induction of CYP1A enzymes is sugges ted mainly to be related to the content of indolyl glucosinolates in these vegetables. The aim of the present study was to evaluate the effects on spe cific CYP activities of various broccoli samples containing different level s of glucosinolates. Groups of rats were fed 1 of 8 broccoli samples from 2 cultivars; grown at different conditions. Thirteen different glucosinolate s were quantified. The content of the 4 major glucosinolate, glucoraphanin (GRAP), glucoiberin, glucobrassicin (GB), and neoglucobrassicin (NeoGB) var ied 5.6-, 2.7-, 3.2-, and 6.6-fold, respectively, among the broccoli sample s. Dietary broccoli induced the CYP1A enzyme activities, 7-ethoxyresorufin- O-deethylase (EROD) and 7-methoxyresorufin-O-demethylase (MROD), in rat liv er, weakly in colon, but not in kidney. In concordance, the hepatic metabol ism of 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP) to the proxim ate carcinogen N-OH-PhIP, a CYP1A-related activity, was enhanced by broccol i. The 7-pentoxyresorufin-O-depenthylase (PROD) activity, an assay for CYP2 B1/2, was weakly induced in colon and kidney but not in liver by broccoli. The 2 beta -OH- and 6 beta -OH-testosterone hydroxylase activities were ind uced in liver microsomes, showing that broccoli increased CYP3A activity. T he observed modulations of CYP activities depended clearly on the broccoli sample used, and significantly different responses were observed for differ ent cultivars and growth conditions. These results indicate that modulation of CYP metabolism by broccoli may vary significantly in humans as well, as the content of glucosinolates and other active substances also varies betw een commercially available broccoli samples. The different effects dependin g on the vegetable sample eaten have to be considered in future experiments and dietary recommendations. Copyright (C) 2001 by W.B. Saunders Company.