Kinetics of hemoglobin and albumin adducts in rabbits subchronically exposed to benzo[a]pyrene

Benzo(a)pyrene diolepoxide-haemoglobin and albumin adducts at low levels of benzo(a)pyrene exposure

A biomonitoring study was conducted to simultaneously measure individual benzo(a)pyrene (BaP) exposure in 50 office employees, not occupationally exposed to polycyclic aromatic hydrocarbons (PAH), using personal samplers and the formation of (+) r-7, t-8-dihyroxy-t-9,t-10-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene (BPDE) adducts to haemoglobin (BPDE-Hb) and serum albumin (BPDE-SA). The population enrolled was exposed to an average of 0.58 ± 0.46 ng BaP m(-3) (mean ± SD). The concentration of BaP collected from smokers' samples was double that from non-smokers (P = 0.007). BPDE adducts to Hb and SA were quantified as BaP tetrols released from hydrolysis of macromolecules and measured by high-resolution gas chromatography-negative ion chemical ionization-mass spectrometry. BPDE-Hb adducts were detected in 16% of the population and BPDE-SA adducts in 28%. Smoking did not affect adduct formation. When BaP personal monitoring data were used as the criterion of exposure, no correlation was found with the presence and the levels of BPDE-Hb and BPDE-SA adducts. Undetected sources of PAH, such as the diet, might markedly alter the exposure profile depicted by individual air sampling and affect the frequency and levels of protein biomarkers. This is the first comparative analysis of BPDE-Hb and BPDE-SA adducts, providing reference values for these biomarkers in a general urban population. However it is difficult to establish which biomarkers would be the more relevant in assessing low BaP exposure, due to undetectable factors such as dietary PAHs, that might have influenced the results to some degree.

In vivo formation of (+)-anti-benzo[a]pyrene diol-epoxide-plasma albumin adducts in fish

Benzo[a]pyrene (BaP), a procarcinogenic polycyclic aromatic hydrocarbon (PAH), is bioactivated to BaP diol-epoxides (BPDEs) that can form adducts with DNA and blood proteins. We report here for the first time the in vivo formation of adducts between BPDE and plasma albumin (Alb) from two fish species experimentally exposed to BaP. Brook trout (Salvelinus fontinalis) received either a single i.p. dose (10 mg/kg) or two separate i.p. doses (25 mg/kg; 7 days apart) of BaP, and blood was collected 2 (single exposure) or 3 (multiple exposure) days post-treatment. Arctic charr (Salvelinus alpinus) received 10 i.p. doses (3 mg/kg; a single dose every 6 days), and blood was collected 2 days after the second, sixth, and 10th injections. BPDE-Alb adducts were measured by an improved HPLC/fluorescence method developed to detect and quantify BaP-tetrols released after acid hydrolysis of adducted Alb. HPLC/fluorescence chromatograms of Alb from BaP-treated fish revealed only BaP-tetrol I-1, thus indicating the formation of adducts exclusively via the (+)-anti-BPDE metabolite. Levels of (+)-anti-BPDE-Alb adduct ranged from 0.68 to 19.6 ng of tetrol I-1 per gram of Alb. Notably, adduct level was not related to BaP dose and there was no accumulation of adducts with repeated exposure, which may indicate a very short half-life (< 2 days) of plasma Alb in fish. The data suggest that BPDE-Alb adducts in fish could be useful as a non-destructive biomarker of recent exposure to bioactivated BaP.

Benzo(a)pyrenediolepoxide-hemoglobin adducts and 3-hydroxy-benzo(a)pyrene urinary excretion profiles in rats subchronically exposed to benzo(a)pyrene

The time profiles of benzo(a)pyrenediolepoxide (BaPDE)-hemoglobin (Hb) adduct formation and 3-hydroxybenzo(a)pyrene (3-OHBaP) urinary excretion were studied in male Sprague-Dawley rats exposed to daily benzo(a)pyrene (BaP) intraperitoneal doses of 1.25, 6.25, and 31.25 mumol/kg administered Tuesday to Friday for 4 consecutive weeks. Blood was withdrawn weekly, on Tuesdays, prior to dosing. Twenty-four-hour urine samples were collected on Mondays (following 72 h without treatment) and Thursdays. Analytes were quantified by high performance liquid chromatography (HPLC)/fluorescence. Exposure to BaP resulted in the accumulation of BaPDE-Hb adducts, reaching an average of 1.2 +/- 0.3, 8.3 +/- 1.9, and 38.2 +/- 6.1 pmol/g Hb for the 1.25, 6.25, and 31.25 mumol/kg per day doses after 4 weeks of treatment. The expected saw tooth excretion profile of 3-OHBaP was observed, with peaks on Thursdays and troughs on Mondays, and showed a progressive rise on both Mondays and Thursdays. Increase in Monday values with time suggested a possible increase in BaP body burden during exposure. To verify this aspect further, the urinary excretion kinetic of 3-OHBaP following acute intraperitoneal dosing (31.25 mumol/kg) was determined. Urine samples were collected at frequent timed intervals for up to 164 h post-dosing. Two-step elimination was observed, the second step having a half-life of 25 h, presumably linked to the slow release of BaP accumulated in fatty tissues upon repeated treatment.(ABSTRACT TRUNCATED AT 250 WORDS)