Effect of exposure to benzo[a]pyrene on SODs, CYP1A1/1A2- and CYP2E1 immunopositive proteins in the blood clam Scapharca inaequivalvis |
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| Authors: | Monari M Cattani O Serrazanetti G P Selli A Pagliuca G Zironi E O'Hara S C M Livingstone D R |
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| Institution: | Department of Biochemistry G. Moruzzi, University of Bologna, Via Tolara di Sopra 50, 40064 Ozzano Emilia, Bologna, Italy. mmonari@vet.unibo.it |
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| Abstract: | The effects of water-borne exposure to benzoa]pyrene (36 h; celite-bound 0.44 mg L(-1) Ba]P) on cytochrome P450 (CYP) and superoxide dismutases (SODs) were examined in digestive gland of the blood clam, Scapharca inaequivalvis. Ba]P accumulation and elimination were rapid, with maximum whole-body concentrations of 1.78 ng g(-1) wet wt after 12 h of treatment, followed by a progressive decline to 0.89 ng g(-1) at 36 h. The presence of Ba]P resulted in an increase in total CYP of digestive gland microsomes from 54+/-14 to 108+/-21 pmol/mg protein (mean+/-SD; p<0.05, 24 h). Increases were also seen in microsomal CYP1A1/1A2-immunopositive protein (50.5 kDa app. mol. wt; p<0.05), but not CYP2E1-immunopositive protein (49 kDa app. mol. wt.), indicating a specific response of the former isoform. Exposure to Ba]P produced a steady increase in Mn-SOD digestive gland activity (p<0.01; p<0.05) but no significant change in Cu/Zn-SOD activity. The respective proteins, measured by western blotting, were not significant induced after Ba]P exposure. Cu/Zn-SOD and Mn-SOD activities were correlated with total CYP levels (r=0.96 and 0.63, respectively), indicating a role for CYP in reactive oxygen species (ROS) production during exposure. Both 'NADPH-independent' and NADPH-dependent metabolism of Ba]P by digestive gland microsomes was seen, producing mainly 1,6-, 3,6- and 6,12-diones, with some phenols and 7,8-dihydrodiol; putative protein adducts were also formed. Redox cycling of the diones may also have contributed to ROS production, leading to the increased SOD activities. |
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