Excretion of benzo[a]pyrene-Gua adduct in the urine of benzo[a]pyrene-treated rats.

A benzo[a]pyrene(BP)-Gua adduct was extracted in the urine of rats treated with BP. Some (0.15%) of the administered dose of BP was excreted as BP-Gua within 48 h. A double labelling experiment demonstrated that the excreted product contained both a BP and a Gua moiety. Partially hepatectomized rats treated with [14C]Gua during the regenerative phase were injected with [3H]BP and the urine collected and processed by chromatographic procedures. The adduct had similar chromatographic properties to the adduct released from human PLC/5 cells treated with 7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) and co-chromatographed with 7-BPDE-Gua released from BPDE-adducted DNA under aqueous conditions. Detection and quantitation of BP-Gua offers an alternative, non-invasive method of monitoring individuals exposed to carcinogenic polycyclic aromatic hydrocarbons (PAHs).

Biological monitoring of polycyclic aromatic hydrocarbons. Metabolites in urine.

Assays of urinary mutagenicity, urinary 3-hydroxy-benzo(a)pyrene, and urinary 1-hydroxypyrene were used to study their suitability in estimating exposure to polycyclic aromatic hydrocarbons (PAH) in coal tar products. Rats exposed to coal tar solutions applied on the dorsal skin excreted mutagens, 3-hydroxy-benzo(a)pyrene, and 1-hydroxypyrene dose dependently in their urine. The correlation between the three parameters was high. Five dermatologic patients undergoing topical coal tar treatment excreted low concentrations of 3-hydroxy-benzo(a)pyrene and high concentrations of 1-hydroxypyrene. A significant correlation between the excretion of the two metabolites was found. The smoking workers of a coal tar distillation plant showed a significantly enhanced urinary mutagenicity compared with their nonsmoking colleagues, but an increase due to occupational exposure was not found. However, the concentration of 1-hydroxypyrene in the urine of these workers highly exceeded the upper 95 percentile of a reference population. The urinary excretion of 1-hydroxypyrene of smoking referents was not significantly increased compared with that of nonsmoking referents. The data suggest that urinary 1-hydroxypyrene is a sensitive and specific marker for the assessment of occupational exposure to PAH.

Excretion of 3-hydroxy-benzo(a)pyrene and mutagenicity in rat urine after exposure to benzo(a)pyrene.

3-hydroxy-benzo(a)pyrene (3-OH-B(a)P) and mutagenic activity in rat urine were determined after the oral administration of benzo(a)pyrene given in three repeated doses of 10, 20 and 50 mumol kg-1. The procedure for the determination of 3-OH-B(a)P consisted of enzymic hydrolysis, separation and HPLC-analysis. The mutagenic activity of concentrated urine samples was assayed with the Salmonella typhimurium strain TA98 in the presence of S9 mix and beta-glucuronidase. The urinary excretion of 3-OH-B(a)P and mutagens showed a correlation and both increased dose-dependently during the sampling period of 6 days. Data indicated that 3-OH-B(a)P can be regarded as a reliable representative of all urinary (pre)-mutagens derived from benzo(a)pyrene and exposure of rats to benzo(a)pyrene could be detected with greater sensitivity by the HPLC assay of 3-OH-B(a)P than with the non-specific mutagenicity assay.

Urinary excretion of 3-hydroxy-benzo[a]pyrene after percutaneous penetration and oral absorption of benzo[a]pyrene in rats.

A method for the monitoring of exposure to benzo[a]pyrene was applied to rat urine samples. Benzo[a]pyrene was administered percutaneously and orally with repeated doses of 10, 20 and 50 mumol/kg body wt. At low dose levels, the urinary excretion of 3-OH-benzo[a]pyrene was higher after percutaneous treatment than after oral administration. The excretion of 4 benzo[a]pyrene metabolites, including 3-OH-benzo[a]pyrene, is faster after oral administration. The percutaneous absorption of small doses of benzo[a]pyrene appears to be greater than the oral absorption.

Percutaneous absorption of [7.10-14C]benzo[a]pyrene and [7,12-14C]dimethylbenz[a]anthracene in mice.

The percutaneous penetration, tissue distribution, and excretion of 14C-labeled benzo[a]pyrene (BaP) and dimethylbenz[a]anthracene (DMBA) were studied in mice. Both BaP and DMBA rapidly penetrated the skin and were excreted more in the feces than in the urine. The proportion of BaP or DMBA absorbed was less with increasing applied dose due to apparent saturation of the uptake process. Uptake from the dorsal skin of the nose was similar to uptake from the dorsal nuchal skin.

Metabolism and urinary excretion of mutagenic metabolites of benzo[a]pyrene in C57 and DBA mice strains.

Groups of C57Bl/6 (B6) mice (responsive) and DBA/2 (D2) (non-responsive) mice received an i.p. dose of benzo[a]pyrene (BP) (100 mg/kg body weight) with or without pretreatment with beta-naphthoflavone (BNF), an inducer of monooxygenases. The amount of mutagenic BP metabolites in the urine was determined by the Salmonella/microsome assay (strain TA100) and excretion of BP metabolites was quantified by h.p.l.c. After inducer treatment, the responsive mice excreted more mutagens and total oxidized BP metabolites in the urine than did the non-responsive strain. The ratio of BP diols:total oxidized metabolites was 0.42 in B6 mice and 0.72 in D2 mice and was not affected by inducer treatment. After a dose of [14C]BP, radioactivity was measured in the faeces for up to 7 days. The half-life of [14C]BP in the non-responsive D2 mice was about twice that in the responsive B6 mice. Our results agreed with a previously proposed model of the risk factors for toxic effects and/or the development of tumours after exposure to polycyclic aromatic hydrocarbons in responsive and non-responsive mouse strains.

Metabolism and excretion of benzo[a]pyrene in the rabbit.

1. Following i.v. administration of [14C]benzo[a]pyrene (3 mumol/kg) to rabbits, 30% of the 14C dose appeared in bile and 12% in urine, within six hours. 2. Biliary and urinary metabolites were mainly conjugated; less than 12% of the 14C was extractable with ethyl acetate, but after treatment with beta-glucuronidase or aryl sulphatase 30-40% became extractable. 3. H.p.l.c. analysis of the extracts indicated that the major non-polar metabolite was benzo[a]pyrene, 9,10-diol (18% of 14C in bile and 24% of 14C in urine, mainly conjugated with glucuronic acid). Smaller amounts of the 4,5-diol, the 3,6-quinone, and the 9-hydroxy- and 3-hydroxybenzo[a]pyrene were also found in bile (total less than 10%), together with 9-hydroxybenzo[a]pyrene and two unknown metabolites (X and Y) in urine (total less than 4%). 4. The proximate carcinogen, the 7,8-diol, was not detected in any extract. 5. After intraduodenal administration of biliary metabolites of [14C]benzo[a]pyrene (approx. 0 X 3 mumol), 14C was excreted in the bile (21% dose) and urine (14%) within 23 h, indicating that metabolites can undergo enterohepatic circulation in the rabbit.