Effects of polchlorinated paraffins on hepatic, renal and intestinal biotransformation rates in comparison to the effects of polychlorinated biphenyls and naphthalenes

Polychlorinated paraffins (PCPs), biphenyls (PCBs) and naphthalenes (PCNs) were compared as inducers of drug‐metabolizing enzymes in different rat tissues. Two different chain lengths (C11 or C20) and chlorination degrees (40 or 70% chlorine) of PCPs, two preparations of PCNs (50–70% chlorine), and one PCB preparation (54% chlorine) were used. The compounds were administered intraperitoneally to rats, and the activities of various drug‐metabolizing enzymes were analysed in hepatic and renal microsomes and in the post‐mitochondrial supernatant of the small intestinal mucosa. PCB and PCNs were potent inducers of both hepatic and renal drug‐metabolizing enzyme activities, whereas PCPs produced only minor changes in these activities. When compared with each other, PCNs were somewhat stronger inducers than PCB. The enhancement of enzyme activities in the liver was different from that of the kidney. The maximal induction of aryl hydrocarbon hydroxylase was 4.8‐fold in the liver and 7.2‐fold in the kidney, that of ethoxy‐coumarin deethylase 12‐fold in the liver and 53‐fold in the kidney, while the activity of UDP glucuronosyl‐transferase was increased only in the liver (maximally 4.5‐fold). In small intestinal mucosa, there were only moderate changes in the activities of drug‐metabolizing enzymes.