recover TCPM-O-sulfonate from TLC plates resulted in recovery of TCPM from the

conjugate band, perhaps because of the conjugate' s instability.

 A study of the sulfonation of PCP was complicated by the fact that it is a known

SULT inhibitor, often with K,s in the submicromolar range. In our experiments, this was

seen as a 74% decrease in formation of the unidentified sulfonate conjugates (band

shown at the solvent front in Figure 3-8) upon addition of 1 CLM PCP. Although PCP was

a strong inhibitor of SULTI1E1 (Kester et al., 2000), and has been postulated to be a dead-

end inhibitor for phenol sulfotransferases (Duffel and Jakoby, 1981), it was possible that

polar bear SULT 1A isoforms were not completely inhibited by PCP, or that other SULT

isoform(s) were responsible for the limited sulfonation activity observed. Thus, we have

shown that, in vitro at least, one mammalian species is capable of limited PCP

sulfonation. Even though the tertiary alcohol of TCPM was a poor candidate for

sulfonation, it was metabolized at twice the efficiency of PCP, which has a phenolic

group that is usually more susceptible to sulfonation. This demonstrates the extent of the

decreased nucleophilicity on the phenolic oxygen due to the resonance delocalization

afforded by the five chlorine substituents.

 Conclusions

 In summary, this study demonstrated that, in polar bear liver, 3-OH-B[a]P was a

good substrate for sulfonation and glucuronidation. Other, chlorinated, substrates were

biotransformed with less efficiency, implying that reduced rates of sulfonation may

contribute to the persistence of compounds such as hexachlorinated OH-PCBs, TCPM

and PCP in polar bear tissues.