Suppression of pulmonary P4502b and induction of hepatic, intestinal and kidney P4501a-1 and 1a-2 in the Ah-responsive and non-responsive mouse by Aroclor 1254

New insight into the perplexing toxic features of PCBs: A study of nephrotoxicity in an animal model

The present study investigated the effects of PCBs on the rat kidneys with attention given to the determination critical effect dose (CED) using the Benchmark dose (BMD) approach. Male albino Wistar rats (7 animals per group) were given by oral gavage Aroclor 1254 dissolved in corn oil at doses of 0.0, 0.5, 1, 2, 4, 8, or 16 mg/kg b.w./day for 28 days. The PCB nephrotoxicity was manifested by a dose-dependent changes in serum urea levels. The study has also revealed PCB-induced oxidative stress induction in kidneys. The observed nephrotoxic effects can be partly explained by oxidative damage of lipids and proteins in the kidneys due to observed reduced CuZnSOD activity and disturbances in antioxidant protection. Аll the renal oxidative stress parameters showed dependence on PCB oral doses as well as internal, measure kidney PCB levels. Calculated BMDL values were lower than estimated no observed adverse effect levels (NOAEL) based on the study, suggesting the importance of BMD approach use in future risk assessment.

Differential in vivo effects of alpha-naphthoflavone and beta-naphthoflavone on CYP1A1 and CYP2E1 in rat liver, lung, heart, and kidney

Male Sprague-Dawley rats were treated intraperitoneally with corn oil, the aryl hydrocarbon receptor (AHR) agonist beta-naphthoflavone (betaNF), or the relatively weak AHR agonist alpha-naphthoflavone (alphaNF). Animals treated with betaNF experienced a significant loss (12%) of total body mass over 5 days and a dramatic elevation of CYP1A1 mRNA in all of the organs studied. Treatment with alphaNF had no significant effect on body mass after 5 days and caused only minor increases of liver, kidney, and heart CYP1A1 mRNA. In contrast, lung CYP1A1 mRNA was increased by alphaNF treatment to levels comparable to that seen with betaNF treatment. CYP2E1 mRNA levels were also elevated in liver, lung, kidney, and heart in response to betaNF treatment, whereas alphaNF was without effect. Large increases of CYP1Al-dependent 7-ethoxyresorufin O-deethylation (EROD) activity occurred with microsomes prepared from the tissues of betaNF-treated animals. Comparatively small changes were associated with alphaNF treatment, with the exception of lung, where EROD activity was increased to approximately 60% of that with betaNF treatment. CYP2E1-dependent p-nitrophenol hydroxylase (PNP) activity was also increased by betaNF treatment in microsomes prepared from kidney (3.1-fold), whereas alphaNF was without effect. In contrast, alphaNF or betaNF treatment caused significant decreases of lung microsomal PNP (72% and 27% of corn oil control, respectively) and 7-pentoxyresorufin O-deethylation (48% and 17% of corn oil control, respectively) activities, indicating that PNP activity may be catalyzed by P450 isoforms other than CYP2E1 in rat lung. We conclude that betaNF and alphaNF have differential effects on the expression and catalytic activity of CYP1A1 and CYP2E1, depending upon the organ studied. These changes most likely occur as a result of the direct actions of these compounds as AHR agonists, in addition to secondary effects associated with AHR-mediated toxicity.