Aryl Hydrocarbon Hydroxylase. Mixed-function oxygenase (MFO) enzymes are important, 

 primarily in the liver, in detoxifying xenobiotics and steroid hormones. Relatively insoluble 

 componds are converted into water-soluble metabolites, which may be excreted or further 

 conjugated and, then, excreted in the urine or bile. Potent inducers of the MFO enzymes 

 include polycyclic aromatic hydrocarbons, PCBs, and petroleum. MFO enzymes include AHH 

 enzymes which were assayed in the present evaluation using benzo(a)pyrene as a substrate. 

 In previous studies of P. stellatus in the San Francisco Bay, relatively high AHH activities 

 were observed in samples most highly contaminated with chlorinated hydrocarbons. Mean 

 AHH activities in fish collected in 1983-1984 from the BK, OK, and SP sites sampled in the 

 present evaluation were 95, 54, and 51 units (pmol 3-OH B(a)p/min/mg protein), respectively 

 (Spies et al, 1985). AHH activities were not suppressed in BK fish during gametogenesis 

 (presumably, in response to exposure to organic contaminants), whereas they were suppressed 

 in SP fish. The effects of AHH-mediated perturbations in the regulation of steroid hormones 

 during and after gametogenesis is unknown, but could be significant in fish reporduction. In 

 San Francisco Bay, high hepatic xenobiotic concentrations and high hepatic AHH activity 

 in P. stellatus were negatively correlated with several measures of spawning success 

 suggesting a cause-effect relationship. Some individual fish from the BK and OK sites had 

 AHH activities of over 300 units (Spies et al., 1985). 



The mean AHH activities (147 to 363 units) recorded in the present study in fish from 

 OK and VJ and in males and immatures at SP were higher than expected, based upon 

 experience from previous studies of the same species. The large difference {e.g., 363 vs. 86 

 units in males and immatures) in activities between OK and BK fish also was unexpected, 

 since the sites are near each other and in previous research the differences in AHH 

 activities between these sites had not been as large. 



Compared to P. stellatus, mean AHH activities in P. americanus from four sites in New 

 England were relatively high (450 to 770 pmol B(a)p metabolites/min/mg protein) and 

 uniform. There was a strong correlation between EROD and AHH activities in fish from the 

 Buzzards Bay site (Stegeman et al., 1987). Hepatic AHH activity in English sole (Parophrys 

 vetulus) ranged from 36 to 330 pmol/mg protein/min in fish from a rural area, Discovery Bay, 

 known to be uncontaminated with aromatic hydrocarbons (Varanasi et al, 1986). Fish from 

 another area in Puget Sound with higher aromatic hydrocarbon concentrations had hepatic 

 AHH activities that ranged from 330 to 570 pmol/mg protein/min. A strong positive 

 correlation was observed in hepatic AHH activity and concentration of specific isozymes of 

 cytochrome P-450. In a subsequent study, Johnston et al. (1988) reported a range of 72 to 492 

 pmol/mg/min in mean AHH activity in P. vetulus from Puget Sound sites, corresponding to a 

 6.8-fold difference between sites. A range of 33.5 ± 21.2 to 90.2 ± 52.2 pmol B(a)p 

 hydroxylase/min/mg protein was reported by Addison and Edwards (1988) for P. flesus 

 sampled along a pollution gradient in Langesundfjord, Norway. This range corresponded to a 

 2.7-fold difference between the least and most induced fish. Nearly a 4-fold difference in 

 response in the same species was recorded following exposure to a dilution series of oil and 

 copper in mesocosm basins. 



Hepatic AHH activity in untreated sheepshead (Archosargus probatocephalus), flounder 

 {Paralichthyes lethostigma), stingray (Dasyatis sabina) and skate (Raja erinacea) averaged 

 3100 ± 1800, 250 ± 90, 770 ± 390 and 180 ± 180 units (50 pmol 3-hydroxybenzo(a)pyrene/ 

 min/mg protein), respectively (James and Bend, 1980). Hepatic AHH activity was inducible 

 with exposure to 3-methylcholanthrene or 1,2,3,4-dibenzanthrene, resulting in an increase in 

 activity of over an order of magnitude in the same species. AHH activity in liver 

 microsomes of the deep-sea fish Coryphaenoides armatus averaged 408 ± 170 units 

 (pmol/min/nmol P-450) in samples from the Hudson Canyon off New York and 0.045 ± 0.010 

 units in samples from the Carson Canyon off Newfoundland (Stegeman et al., 1986). PCB 

 concentrations in the fish livers were roughly 8 times higher in the Hudson Canyon than in 

 the Carson Canyon. 



Gender-specific and species-specific differences in AHH activities were observed in 

 sanddabs collected in Southern California (Spies et al, 1982). Specific activities were 

 usually higher in males and about an order of magnitude higher in Citharichthys sordidus 

 than in C. stigmaeus. Fish collected during the winter had lower activities than those 



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