Table 41. Average CV and range/average SD for total micronuclei counts in Platichthys 

 stellatus from San Francisco Bay (present study), Pseudopleuronectes antericanus from 

 New England (Longwell, 1983), Genyonemus lineatus from southern California (Hose et 

 ah, 1987), and Paralabrax clathratus from southern California (Hose et al., 1987). 



Platichthys Pseudopleuronectes Genyonemus Paralabrax 



stellatus (5 sites, americanus (27 sites, lineatus (2 sites, clathratus (2 sites, 



n=12 to 15 fish at n = 2 to 20 fish at n = 28 fish at n = 15 fish at 



each site) each site) each site) each site) 



Average CV 140.5% 81.2% 108.4% 87.5% 



Range/average SD 1.4 4.94 0.96 2.17 



Micronuclei incidence in fish from all the sites in San Francisco Bay Bay was higher 

 than in fish from coastal reference areas, however, there were no significant differences 

 among sites within San Francisco Bay. Differences among sites in San Francisco Bay could 

 have been expected, since the concentrations of chlorinated organic compounds in the fish 

 differed among sites there. However, the formation of micronuclei may not be responsive to 

 the measured analytes. They may be responsive to compounds such as aromatic hydrocarbons 

 {e.g., B(a)p), which were not quantified in the fish and which are probably readily 

 metabolized to compounds that are not readily quantified. Also, because of its shallow 

 geomorphology and strong water currents, chemical contaminants are readily dispersed 

 throughout the estuary. The concentrations of chemicals rarely show large gradients among 

 the basins of the estuary, but do indicate elevations of most chemicals only in the 

 peripheral harbors and industrial waterways (Long et al., 1988). Therefore, the fish 

 collected at the sites in the estuary may have been exposed to relatively similar 

 concentrations of mutagenic compounds and these concentrations may have been higher than 

 those in fish from outside the estuary. In conclusion, it appears that the incidence of 

 micronuclei is a relatively sensitive measure, that it has been successfully used in several 

 species of marine animals and the data correlated with the concentrations of some organic 

 compounds, but the data are relatively variable among fish captured at the same site. 



Cytochrome P-450. The cytochrome P-450 proteins catalyze monooxygenase reactions. They 

 are the enzymes primarily responsible for metabolism or biotransformation of organic 

 pollutants. This metabolism of xenobiotics can result in their inactivation and detoxification 

 or their activation to toxic derivatives. Inactivation can lead to enhanced elimination and 

 tolerance; activation can lead to serious organ dysfunction or pathology. Cytochrome P-450 

 enzymes are also responsible for both synthesis and degradation of steroid hormones. 

 Aromatic hydrocarbons and chlorinated hydrocarbons, such as PCBs, can induce cytochrome 

 P-450 activity. Cytochrome P-450 exists in different isozymes each having differing 

 functions. One isozyme that has been isolated from fish hepatic microsomes is cytochrome P- 

 450E (Klotz et al, 1983), which appears to be inducible by PAH/PCB-type chemicals. 

 Cytochrome P-450E is likely an important isozyme in conducting EROD activity. 



The background or uninduced levels of cytochrome P-450 activity have been measured in 

 a variety of fish and invertebrates. For example, Stegeman and Kloepper-Sams (1987) 

 reported levels ranging from 0.10 to 0.91 nmol/mg protein in mussels, crustaceans, fish, and 

 rats. Average cytochrome P-450 content in four species of untreated fish ranged from 0.11 to 

 0.50 nmol/mg protein (James and Bend, 1980). In the latter study, exposure to 3- 

 methylcholanthrene or 1,2,3,4-dibenzanthracene resulted in minimal or no change in total 

 cytochrome P-450 content. In the present study, the lowest mean level of total P-450 content 



89 



