hepatic ethoxyresorufin o-deethylase activity of liver microsomal cytochrome p-450 (cyp1a1) in young and adult rats treated with paracetamol and β-naphthoflavone

background: age-related differences in the ethoxyresorufin o-deethylase (erod) activity of cyp1a1 and its inducibility in rats may determine the toxic potential of acetaminophen.  this study was carried out to compare the effects of acetaminophen (apap) and β-naphthoflavone (βnf) on cyp1a1 activity in young and adult rats. methods: for this purpose, young and adult rats (n = four / group) were treated with different doses of apap. likewise groups of young and adult rats were treated with a single dose of β-naphthoflavone (βnf, 67 mg / kg b.w). erod was measured in microsomal fraction using resorufin as the substrate. results:the results showed that a single i. p. injection of apap (25 mg / kg b.w.) failed to alter liver microsomal erod in young and adults. whereas, in adults treated with 250 and 450 mg apap / kg b.w, liver cyp1a1 was elevated to about 45 and 60% respectively. the rate of cyp1a1 induction in young rats with single dose of apap (450 mg/kg b.w) was approximately 32%. induction in cyp1a1 was noticed 4 h after apap injection and returned to normal levels in 24 h. the inducibility of cyp1a1 in rats treated with a toxic dose of apap was comparable to the data obtained from animals treated βnf, 67 mg / kg b.w. conclusion: these results together with our previous reports indicate a similar pattern of changes in cyp1a1 in both the age-groups treated with toxic doses of apap may suggest that the inducible cyp1a1 can equally contribute to protection against liver damage in young and adult rats.