Little is known in terms of multi-matrix cytochrome P450 activity induction under repeated oral exposure
to planar halogenated and polycyclic aromatic hydrocarbons (PHH, PAH). In the present study, 60
rats were daily exposed, during 28 days, to oral ingestion of a mixture consisting of phenanthrene, pyrene
and benzo(a)pyrene at 0, 6 or 600 lg/day. EROD activity, reflecting almost exclusively CYP1A1 and
CYP1B1 activities, was measured in brain and liver microsomes as well as in peripheral blood lymphocytes
(PBLs). All induction kinetics could be appropriately fitted using logistic-like models. After 28 days
of exposure to a 6 lg/day dose, EROD activity was found to be 91, 152 and 94-fold increased in lymphocytes,
liver and brain, respectively, compared to day 0. Plateau activities could be appropriately fitted versus
ingested doses using Hill or Michaelis–Menten models. Correlations between matrices made it
possible to conclude that EROD activity in PBL should be considered as a sensitive, convenient and
non-destructive approach for (i) evaluating EROD activity in liver, which was found to represent 98%
of the observed EROD activities in the three tested matrices and (ii) evaluating oral exposure of homogeneous
groups of farm animals (race, diet) to CYP inducing PAH and PHH.