METANIL-YELLOW - A BIFUNCTIONAL INDUCER OF HEPATIC PHASE-I AND PHASE-II XENOBIOTIC-METABOLIZING ENZYMES

Metanil yellow, a non-permitted food colour, has been found in various foodstuffs. The induction potential of metanil yellow on hepatic micr osomal cytochrome P-450 (P-450)-dependent monooxygenases and cytosolic detoxification enzymes, namely, glutathione S-transferase (GST) and q uinone reductase (QR), was investigated. Oral administration of metani l yellow (430 mg/kg body weight) to four animals for seven days caused significant induction of hepatic P-450 (48%) and its dependent aryl h ydrocarbon hydroxylase (100%) activity and cytosolic GST (136%) and QR (92%) activities. Parenteral administration of metanil yellow (80 mg/ kg body weight) to another set of four animals for 3 days resulted in higher induction of ethoxyresorufin-O-deethylase (228%) as compared to other monooxygenases (64-92%), while GST and QR were also found to be induced (59-95%). Spectra of metanil yellow-induced microsomes showed an increase in P-450 with a shift of 2.2 nm in the soret region. The results suggest that metanil yellow acts as a bifunctional inducer of specific isozymes of P-450 and cytosolic enzymes and thus may involve the cytosolic aryl hydrocarbon (Ah) receptor for this type of inductio n. (C) 1997 Elsevier Science Ltd.