PAH metabolism

Madsen EL, CT Thomas, MS Wilson, RL Sandoli, SE Bilotta (1996b) In situ dynamics of aromatic hydrocarbons and bacteria capable of PAH metabolism in a coal tar-waste-contaminated field site Environ Sci Technol 30 2412-2416. 

Are as well equipped as mammals with liver PAH-metabolizing enzymes... 

One of the strategies applied to enhance the degradation of specific PAH is to offer bacteria one or more known inducers to stimulate both selective growth of PAH degraders and induction of PAH metabolism [38, 73,132,148,182,194], However, little has been reported on the regulation of PAH metabolism by bacteria for compounds other than naphthalene. The transformation of benz[a]-anthracene was found to be inducible by salicylate [188] in a strain that has recently been identified as Sphingomonas yanoikuyae [172], but little else is known about the regulation of the metabolism for HMW PAH. 

In general, the study suggested that Pseudomonas saccharophila P15 expressed a low level of constitutive PAH metabolism which was inducible to much higher levels and that HMW PAH metabolism by this microorganism was induced by the low-molecular weight substrates phenanthrene and salicylate. 

Studies on the consequences of stereoselective PAH metabolism in respect to mutagenicity and carcinogenicity were also shown to be strongly dependent on the relative and absolute configuration of the PAH metabolite (Conney, 1982 Thakker et al., 1982). For example, (-)-7R,8R-dihydrodiol benzo[a]pyrene has a 10-foId higher tumor-initiating activity in female CD-I mouse skin than the (+)-7S,8S-enantiomer, and it produces... 

Fish cell lines used to study PAH metabolism and metabolic activation to toxic compounds... 

The metabolism of PAHs has been studied extensively in vitro and in vivo. The most commonly used system is the rat liver microsomal fraction, although other species are also used. Cells and cultured tissues from human and other animals have also significantly contributed to the elucidation of the PAH metabolic scheme. 

PAH metabolism has been extensively reviewed in human and animal tissue homogenates, cultures, and perfused systems (Autrup et al. 1978 Cavalieri et al. 1987 Cohen et al. 1976 Kiefer et al. 

It is evident in both human and animal studies that hydroxylation is a principal oxidative pathway of PAH metabolism, and consequently, coal tar creosote metabolism. In these studies, there were no discussions to suggest that the researchers attempted to identify other metabolites. 

Dietary exposure to PAH was examined in more detail in a controlled CB beef feeding experiment in which each individual served as his own control. Two individuals exhibited measurable increases in PAH-DNA adduct levels while the two other individuals did not respond. This difference could be due to interindividual differences in constitutive or induced physiological parameters such as absorption, digestion, metabolism, excretion and DNA adduct formation and repair (11). Conney et al (12) demonstrated the induction of phenacetin metabolizing enzymes in human volunteers fed CB beef for four days. Variation in the Inducibllity of PAH metabolizing enzymes in hepatocytes and peripheral blood cells in individuals fed CB beef may explain some of the observed interindividual differences in this study. Other studies (13.14) have demonstrated a 3-10 fold variation in the ability of cultured human lymphocytes or monocytes to form B(a)P-DNA adducts after treatment with B(a)P. 

Next to the limited analytical information available from studies of PAH-metabolism, there is a surprising lack in the current literature of research data on analytical methods for polar PAH-derivatives in environmental samples, e.g. epoxides, phenols, nitroarenes, which may be of great toxicological significance. 

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