Age- and sex-related changes in epoxide hydrolase, UDP-glucuronosyl transferase, glutathione S-transferase, and PAPS sulphotransferase in Sprague-Dawley rats.

1. Age- and sex-related patterns in the activity of hepatic phase 2 conjugating enzymes have been studied in Sprague-Dawley (CD) rats. 2. Epoxide hydrolase activity with styrene oxide ranged from 75 to 346 nmol/min per g and increased with age in males, peaking at week 78. In females, activity remained constant, about 80 nmol/min per g. 3. UDP-glucuronosyl transferase activity with p-nitrophenol ranged from 480 to 1050 nmol/min per g; maximal activity was at week 39. Males had greater activity at weeks 12 to 39. Activity with chloramphenicol ranged from 3.8 to 10.3 nmol/min per g with no consistent age or sex relationship. 4. Glutathione S-transferase ranged from 9.5 to 23.6 mumol/min per g with p-nitrobenzyl chloride and from 29.1 to 66.8 mumol/min per g with 1-chloro-2,4-dinitrobenzene, peaking at week 51 with both substrates. Males had greater activity from weeks 12 to 78. 5. Reduced glutathione varied between 3.2 and 6.5 mumol/g, with males tending to have higher concentrations than females and older rats (greater than 39 weeks) having slightly lower concentrations. 6. PAPS sulphotransferase ranged from 190 to 338 nmol/min per g, with maximal activity at week 78 with no consistent sex-related differences.