Effect of dietary lipid on benzo(a)pyrene metabolism by perfused rat liver

Male Holtzman albino rats weighing 60-75 gm were fed purified synthetic diets containing casein (18%), alphacel (4%), wheat starch (44%), sucrose (26%), Jones Foster salt mix (4%), and vitamin mix (4%) for three weeks. The diet for group I contained no fat, whereas corn oil (10%) substituted for 10% sucrose in the diet for group II. All animals were administered 3-methylcholanthrene [20 mg/kg intraperitoneally (ip) in 0.5% methylcellulose solution] for two successive days prior to sacrifice in order to increase the activity of the mixed function oxidase (MFO) responsible for metabolizing benzo(a)pyrene [B(a)P]. After 21 days on diet, livers were perfused with benzo(a)pyrene in blood-free Krebs Henseleit bicarbonate buffer containing 100 mg glucose plus 200 units of heparin per 100 ml. Aliquots of perfusate were removed at five, ten, 20, 30, 40, and 60 minutes for analysis of B(a)P metabolites. Higher concentrations of B(a)P-9, 10-dihydrodiol; B(a)P-4,5-dihydrodiol; B(a)P-7,8-dihydrodiol; and 3-hydroxy B(a)P were recovered from livers of rats fed the diet containing 10% corn oil than from livers of rats fed the fat-free diet. The concentrations of 9-hydroxy B(a)P except the 9,10-dihydrodiol were recovered from bile along with two unidentified metabolites. Following the perfusion period, homogenized and extracted livers from rats fed the diet containing corn oil retained significantly higher concentration of the three dihydrodiols and two phenols than livers from rats fed the fat-free diet.