Correlation between cytochrome p450 2b1 induction by barbiturates and toxicity in the chick embryo in ovo

Using the highly sensitive probe‐substrate pentoxyresorufin towards cytochrome P450 2B1 isozymes, the relationship between the induction of this set of hemoproteins by barbiturates and toxicity was studied. Each chemical, allobarbital (AB), amobarbital (AM), barbital (BA), butobarbital (BB), buthetal (BU), cyclobarbital (CB), heptobarbital (HE), hexobarbital (HX), mephobarbital (ME), pentobarbital (PA), pentotal (PT), phenobarbital (PB), secobarbital (SE) and vinbarbital (VB) was injected in the chick embryo at the 16–18 day of embryonic incubation in equivalent doses (50, 25, 12.5, 6.25 and 3.12% of the respective LD50) and the mixed function monooxygenase activity examined in purified hepatic microsomes. For each barbiturate, linear regression was performed for both the inductive and toxic slope related to P450 2B1‐like activity in order to evaluate the IC100 in μmol/egg [the dose producing a 100 % increase of pentoxyresorufin dealkylation (PROD) during the induction phase] and the TC100, (the dose prod...