Amount and type of dietary lipid modulate rat hepatic cytochrome P-450 activity

The influence of the amount and type of dietary lipid on rat hepatic cytochrome P-450 activities in the presence and absence of inducer administration was investigated. Weanling male Sprague-Dawley rats were fed fat-free or 20% beef tallow, olive oil, corn oil, linseed oil, or menhaden oil diets in combination with one of the following three treatments: no inducer, intraperitoneal injection of phenobarbital (75 mg/kg body wt) for three consecutive days before they were killed, or intragastric administration of acetone (5 ml/kg) one day before they were killed. Twenty percent linseed oil and menhaden oil diets induced the highest level of activity among the different fat types in the presence of phenobarbital and acetone. Cytochrome P-450IIB1 activity was induced to a significantly greater extent by acetone administration in conjunction with the 20% menhaden oil diet than in conjunction with the other dietary oils (p < 0.05). In the presence of acetone, 20% beef tallow, 20% linseed oil, and 20% menhaden oil diets significantly induced cytochrome P-450IIE1 activity compared with the fat-free diet (p < 0.05). In conclusion, cytochrome P-450IIB1 and P-450IIE1 activities in rats were significantly increased by specific inducers, and dietary lipid was necessary for this effect. Diets supplemented with linseed and menhaden oils were most effective in inducing this activity.