Effect of exposure to benzo[a]pyrene on SODs, CYP1A1/1A2- and CYP2E1 immunopositive proteins in the blood clam Scapharca inaequivalvis.
The effects of water-borne exposure to benzo[a]pyrene (36 h; celite-bound 0.44 mg L(-1) B[a]P) on cytochrome P450 (CYP) and superoxide dismutases (SODs) were examined in digestive gland of the blood clam, Scapharca inaequivalvis. B[a]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 B[a]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 B[a]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 B[a]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 B[a]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.
Monari
M
M
Department of Biochemistry G. Moruzzi, University of Bologna, Via Tolara di Sopra 50, 40064 Ozzano Emilia, Bologna, Italy. mmonari@vet.unibo.it
Cattani
O
O
Serrazanetti
G P
GP
Selli
A
A
Pagliuca
G
G
Zironi
E
E
O'Hara
S C M
SC
Livingstone
D R
DR
D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000032:analysis / Q000187:drug effects*; D001564:Benzo(a)pyrene / Q000032:analysis / Q000633:toxicity*; D015153:Blotting, Western; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis; D004781:Environmental Exposure; D008861:Microsomes / Q000201:enzymology; D049894:Scapharca / Q000187:drug effects* / Q000201:enzymology; D012623:Seawater; D013482:Superoxide Dismutase / Q000032:analysis / Q000187:drug effects*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
D014874:Water Pollutants, Chemical; D001564:Benzo(a)pyrene; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; D013482:Superoxide Dismutase