Cytochrome EROD activity

Tributyltins and other organotins induce chromosomal aberrations in mammals, although this was not observed in tests with aquatic invertebrates (Dixon and Prosser 1986). Studies with isolated rat hepatoma cells, TBT, and PCB 126, show that TBT inhibits cytochrome P-4501A activity, and PCB 126 induces EROD activity. However, PCB-induced EROD activity was potentiated by coexposure to low noncytotoxic concentrations of TBT (Kannan et al. 1998b). Authors concluded that TBT does not interfere with Ah receptor binding and that potentiation of EROD activity and cytotoxicity as a result of coexposure to PCB 126 and TBT is significant because they coaccumulated in a variety of marine organisms. 

Scup, Stenotomus chrysops injected intraperitoneally with 1,5, or 10 mg/kg BW of PCBs 77, 105, 118, 128, or 138 and examined tor increases in ethoxyresorufin O-deethylase (EROD) activity, immunodetectable cytochrome P-450E (the EROD catalyst in scup) and in vitro translatable mRNA for P-450E... 

Sediments and biota collected from the Hersey River, Michigan, in 1978, were heavily contaminated with phenanthrene, benz[a]anthracene, and benzo[a]pyrene when compared to a control site. Elevated PAH concentrations were recorded in sediments, whole insect larvae, crayfish muscle, and flesh of lampreys (family Petromyzontidae), brown trout (Salmo trutta), and white suckers (Catostomus commersoni), in that general order (Black et al. 1981). The polluted collection locale was the former site of a creosote wood preservation facility between 1902 and 1949, and, at the time of the study, received Reed City wastewater treatment plant effluent, described as an oily material with a naphthalene-like odor (Black et al. 1981). In San Francisco Bay, elevated PAH concentrations in fish livers reflected elevated sediment PAH concentrations (Stehr et al. 1997). In Chesapeake Bay, spot (Leiostomus xanthurus) collected from a PAH-contaminated tributary (up to 96 mg PAHs/kg DW sediment) had elevated cytochrome P-450 and EROD activity in liver and intestine microsomes (Van Veld et al. 1990). Intestinal P-450 activity was 80 to 100 times higher in fish from highly contaminated sites than in conspecifics from reference sites intestinal EROD activity had a similar trend. Liver P-450 and EROD activity was about 8 times higher in spot from the contaminated sites when compared to the reference sites. Liver P-450 activity correlated positively with sediment PAH, but intestinal P-450 activity seemed to reflect dietary exposure (Van Veld et al. 1990). The poor correlation between hepatic concentrations of PAHs and P-4501A is attributed to the rapid metabolism of these compounds (van der Weiden et al. 1994). 

BaP alone produced glycogen depletion in liver cadmium alone caused hepatic perivascular fibrosis. Mixture produced complete disorganization of the hepatic parenchyma, including nuclear degeneration higher increase in EROD activity (by 19-fold), BaP hydroxylase activity (by 71-fold), and cytochrome P-450 microsomal content by 2-fold... 

After 72 h, bile contained 25% of the total radioactivity major BaP metabolites were glucuronides (54%), sulfates (12%), and unmetabolized BaP(14%). The potentially genotoxic metabolite BaP-7,8-dihydrodiol and its glucuronide represented 0.7 and 2.0%, respectively, of the bile radioactivity BaP and chrysene were most efficient in elevating EROD activities, cytochrome P-4501 A protein levels, and total cytochrome P-450 content 1-14 days postinjection. Less pronounced increases were caused by fluoranthene and pyrene B[gh/]PER did not affect these parameters... 

The measurement of the ethoxyresorufin-O-deethylase (EROD) activity is another sensitive parameter to detect the effects of paper mill industrial effluents on living organisms in the receiving waters. The EROD activity is a measure of the activity of the cytochrome P-450 enzyme system, which plays a central role in the transformation and elimination of xenobiotics. Increased EROD activity has been shown as far as 40 km from pulp mills, and EROD induction in fish caused by pulp mill effluents remains after biological treatment [60]. It is specified that EROD activity and erythrocytic nuclear abnormalities are induced by abietic and dehydroabietic acid [60]. 

Several PAHs and hydroxylated or methylated PAH derivatives induce oestrogenic or dioxin-like (antioestrogenic) effects in fish and mammalian cell lines (Santodonato, 1997 Villeneuve et al., 2002 Michallet-Ferrier et al., 2004). For instance, benz[u]anthracene and dibenz[u/2]anthracene elicit oestrogenic responses in vitro (Villeneuve et al., 2002). These two PAHs and five others may also elicit dioxin-like responses, as shown by their induction of ethoxyresorufm-D-deethylase (EROD) activity, a biomarker for cytochrome P450 lAl (Gravato Santos, 2002 Villeneuve et al., 2002). 

Although the role of cytochrome P450 in the metabolism of carbofuran has not been explored in any system, the metabolism of ethyl carbamate by P450 2EI has been reported by Lee elal. (1998). The study implicated cytochrome P450 2EI and carboxylcsterase enzyme in the metabolism of carcinogens such as ethyl carbamate in the murine liver microsomal system. The fish taken from a lake in Newfoundland with a history of hydrocarbon pollution showed increased AHH activity (Payne and Penrose, 1975). Thus, many workers have studied the EROD activity of fish in laboratory conditions or naturally exposed samples as a molecular biomarker for aquatic pollution. These studies are reviewed by Whyte etal. (2000) and Goldfarb el al. (1998), In addition, EROD activity in carbofuran-lreated fish has been measured in laboratory conditions. 

Mammal-derived TEFs underestimate the potency of planar PCB mixtures in fish. TEE values of non-ortho PCB congeners based on mortality of rainbow trout in early life stages are as much as 1000 times lower than TEFs proposed for human risk assessment. TEFs for PCBs were compared using cytochrome P4501A1 induction measured as EROD activity in a rainbow trout liver cell line and in a rat hepatoma cell line. EROD activity in trout liver cells was induced only by PCBs 77, 81, 118, and 126 under normal growth conditions, and in some cultures with PCBs 105,156, and 169. The trout TEFs were 0.023 for PCB 126, 0.064 for PCB 81,0.0034 for PCB 77,0.00016 for PCB 169, and 0.000017 for PCB 118 TEFs for PCBs 105 and 156 were <0.00003. In rat cells, however, all seven PCBs clearly induced EROD activity. It was concluded that the toxic impact of PCBs on rainbow trout is overestimated by risk assessment TEFs based on... 

ClPAHs may be toxic to humans, and they have an equally important impact on the environment because several ClPAHs have also been found to exhibit mutagenic activity in Salmonella typhimurium in the Ames assay [229], To comprehensively estimate reactivity-activity for representative ClPAHs (see Fig. 6) on human and environmental species, Table 5 presents the ethoxyresorufin-O-deethylase (EROD) activities for binding substrates of chlorinated polycyclic aromatic hydrocarbons (ClPAHs) with aryl hydrocarbon receptors (AhRs) in the cytochrome... 

Figure 6.6 Comparison of liver-specific functions such as albumin secretion (a), ammonia elimination (b), and EROD activities (c) in AL and AL/GC sponges for monoculture and co-culture of hepatocytes with NIH3T3. (a) Albumin secretion rates for both systems were measured over 28 days in culture. ELISA specific for mouse albumin were used to quantify protein in 24h conditioned medium, (b) Ammonia elimination was compared between both systems on day 5 and 16 of culture, (c) EROD deethylase activity by cytochrome P4501A1 was compared between both systems on day 6 and 16 of culture. EROD activity was measured using the highly fluorescent resomfin in both systems. All data are represented as mean SDj jj (n = 6). Statistics (two-tailed paired Smdent s f-test) compared monoculture with co-culture P<0.05 and "P <0.01.

Figure 2 Effects of i.p.-injectedpolysaccharides on the level and activity of cytochrome P450s (CYPs). Mice were intraperitoneally administered polysaccharides and /or MC as described in Figure 1. (A) Microsomal proteins were prepared from the liver, and the total CYP contents and (B) the ethoxycoumarin O-deethylation (ECOD) and (C) ethoxyresorufin O-deethylation (EROD) activities were measured as described in Materials and...

Continuous exposure to diets containing PCBs from Saginaw Bay carp induced cytochrome P-450 activity in a dose-dependent manner. Cytochrome P-450 activity in animals switched to the control diet from the PCB-containing diet was the same as controls. EROD hepatic activity is a potential biomarker for current exposure to PCBs and other similar cytochrome P-450 inducers... 

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