Comparative metabolism of benzo(a)pyrene by ovarian microsomes of various species

Abstract

Knowledge of the ability of the female reproductive system to metabolize polycyclic aromatic hydrocarbons (PAHs) is critical to the diagnosis and management of female infertility and for risk assessment purposes. The PAHs are a family of widespread pollutants that are released into the environment from automobile exhausts, cigarette smoke, burning of refuse, industrial emissions, and hazardous waste sites. In exposed animals, PAHs become activated to reactive metabolites that interfere with target organ function and as a consequence cause toxicity. The extent of susceptibility to PAH exposure may depend on the ability of animals to metabolize these chemicals. The present study has been undertaken to assess whether any differences exist among mammals in the metabolism of benzo(a)pyrene (BaP), a prototypical PAH compound. Microsomes isolated from the liver and ovaries of rats, mice, goats, sheep, pigs, and cows were incubated with 5 lM BaP. Postincubation, samples were extracted with ethyl acetate and analyzed for BaP/metabolites by reverse-phase HPLC with fluorescence detection. The rate of metabolism (pmol of metabolite/min/mg protein) was found to be more in liver than in ovary in all the species studied (P \ 0.05). The differences in metabolite concentrations were statistically significant (P \ 0.0001) among the various species in both organs studied. Multiple species comparison also revealed that the differences were statistically significant (P \ 0.001) between rodents (rat and mouse) and higher mammals (ewe, sow, and cow). Even among the higher mammals, in a majority of the cases, the differences in metabolite concentrations were significantly different (P \ 0.001) both in ovary and liver. The BaP metabolites identified were 4,5-diol; 7,8-diol; 9,10-diol; 3-hydroxy BaP; and 9-hydroxy BaP. The rodent microsomes produced considerably higher proportion of BaP 4,5-diol and 9,10-diol than did cow, sow, goat, and sheep. However, microsomes from higher mammals converted a greater proportion of BaP to 3-hydroxy and 9-hydroxy BaP, the detoxification products of BaP. Overall, our results revealed a great variation among species to metabolize BaP. # 2008 Wiley Periodicals, Inc. Environ Toxicol 24: 603-609, 2009

Tissue-Specific Metabolism of Benzo[a]pyrene in Rainbow Trout (Oncorhynchus mykiss): A Comparison between the Liver and Immune Organs

“…Preparation was done according to Harris et al (2009), and aliquots were stored frozen at 280°C until use for experiments. Microsomal protein content was determined according to the method of Bradford (1976).…”

“…Microsomal incubations and extraction for metabolism studies were performed as described previously (Harris et al, 2009 for microsomal incubation; Stuchal et al, 2006 for extraction). The in vitro metabolism assay was performed with microsomal protein concentrations of 0.5 mg/ml and substrate concentration of 5 mM BaP.…”

“…The extended incubation period for microsomes from immune tissues was selected to obtain sufficient amounts of metabolites. The reactions were stopped by addition of 5 ml of ethyl acetate/acetone (2:1); afterward, they were extracted (Stuchal et al, 2006;Harris et al, 2009). The organic phase, including metabolites, was dried down under nitrogen, dissolved in acetonitrile, and analyzed in the HPLC.…”

Differential gene expression analysis of benzo(a)pyrene toxicity in the clam, Ruditapes philippinarum

“…The metabolic process of BaP in vertebrates was studied more clearly than that in invertebrates (Barhoumi et al, 2011;Cavalieri and Rogan, 1995;Harris et al, 2009;Jacques et al, 2010;Ramesh et al, 2001). It has been reported that once BaP enters the cells of mammals, it can be oxidated to various BaP epoxides and phenols catalyzed by cytochrome P450 (CYP450).…”

“…Studies on the toxicity of PAHs are focused on several fields such as genotoxicity, hepatotoxicity, developmental toxicity, carcinogenesis and others (Barhoumi et al, 2011;Harris et al, 2009;Jacques et al, 2010;Wang and Jin, 2010), the toxicity effects of PAHs have been detected from a wide range of organisms (Song et al, 2011;Yin et al, 2011;Pan et al, 2008;Wang et al, 2011b;Tuvikene, 1995;Zhang et al, 2009;Kannan and Perrotta, 2008). It is reported that PAHs can cause harmful effects on the skin, body fluids, and the human ability to fight disease after both short-and long-term exposure (U.S. Department of health and human services, 1995).…”