'-- a Vmax (int)
 g a Vmax (liv)









 1.360 1.385 1.410 1.435
 ovality




Figure 4-5. Relationship between Vmax for OH-PCB glucuronidation in intestine and liver
 and ovality

 Discussion

 In comparison to catfish intestine, catfish liver displayed higher rates of

glucuronidation of OH-PCBs, however both organs collectively biotransform the OH-

PCBs studied with similar efficiency. This occurred because while the glucuronidation

Vmax in the intestine was lower than in the liver, the affinity of intestinal UGTs for the

OH-PCBs was higher than liver UGTs. However, the efficiency of glucuronidation of 4'-

OHCB69 was seven times higher in the proximal intestine; when the data for this

substrate was excluded, the efficiency of glucuronidation was significantly higher

(p=0.01) in liver.

 The total UGT capacity in the liver is much greater than in intestine when the total

content of microsomal protein in these two organs is taken into consideration. In fact, the

levels of microsomal protein from liver were always higher than in the intestine of each

individual fish studied, possibly because of the decreased amount of endoplasmic