Effects of dietary inducers on rat small intestinal cytochrome P-450IA1

There is a falling longitudinal gradient of P-450IA1 along the length of the small intestine of rats fed a stock diet or a BNF-containing diet. In rats fed a special diet, based on purified ingredients, the gradient was abolished but could be restored by addition of betanaphthoflavone (BNF) to the diet. This indicates that the distribution of P-450IA1 in the rat small intestine is regulated by dietary components. Tape-section autoradiographic analysis showed that exposure to dietary BNF was an important determinant for the disposition of ¹⁴C-Trp-P-1. Following dietary BNF treatment, a pronounced retention of radioactivity was observed in the epithelium of the oral cavity, esophagus, forestomach and small intestine, but not in the glandular stomach. This was obvious but less striking in rats given BNF intraperitoneally, whereas no retention could be observed in the gastrointestinal tract of untreated rats.