exhibited tissue-specific expression in plaice (Clarke et al., 1992c). UGTIB2 mRNA has

recently been sequenced from marbled sole (Pleuronectes yokohamnae) liver (AN:

ABl20133), and a partial sequence of an unidentified UGT isoform has been obtained

from the orange-spotted grouper (Epinephehis coioides) (AN: AY735003). The existence

of a number of partial length sequences of UGT homologues from zebrafish (Dario rerio)

EST projects in GenBank provide evidence for the cDNA of 10 distinct UGTs. The

absence of cDNAs with the same 3'sequence and dissimilar 5-exon 1 coding sequence

suggests the absence of alternative splicing of UGTIA genes as seen in mammals. Thus,

George and Taylor (2002) have suggested the existence of three family 1-related UGTs

and another two related to the UGT 2 family in the zebrafish. In general, however, it

appears that fish possess multiple UGTs with similar functional and structural properties

to mammalian UGT.

 Toxicologically, it is important to know whether xenobiotic pollutants such as

PAHs compete with steroids or bilirubin for the same active site on UGT, resulting in

physiological perturbations in reproductive and/or liver function. For example, Atlantic

salmon (Salmo salar) suffering from a multiple pollutant-induced j aundice were shown to

have decreased bilirubin UGT activity (George et al. 1992). Channel catfish are also

exposed to pollutants (such as PAHs and PCBs) which accumulate in sediments. Thus,

this organism may be a useful indicator of the bioavailability of these pollutants in such

sedimentary environments. In addition, the use of this Hish in aquaculture makes it

essential to understand every aspect of its detoxification mechanisms, since these will

ultimately impact human health.