TABLE 1

Kinetic constants for the GST-catalyzed reaction of CDNB and DCNB in rat liver cytosol

GST activity measurements were carried out at 37°C, using 10 µg protein for CDNB and 1 mg protein for DCNB. Each reaction used 1 mM GSH in the presence of varied substrate concentrations.

SubstrateRat age, sex100 mg/kg sodium acetate100 mg/kg sodium DCA
KmVmaxKmVmax
mMnmol/min per milligrammMnmol/min per milligram
CDNBYoung female0.33 ± 0.184568 ± 28010.25 ± 0.207205 ± 2808**
Young male0.22 ± 0.083724 ± 9560.37 ± 0.228506 ± 2258**
Adult female0.28 ± 0.034165 ± 8130.20 ± 0.02****5182 ± 1213
DCNBYoung female0.52 ± 0.0559 ± 130.48 ± 0.04104 ± 12**
Young male0.49 ± 0.0974 ± 30.51 ± 0.0998 ± 6**
Adult female0.56 ± 0.0729 ± 50.55 ± 0.0564 ± 8***
  • The data are expressed as the means ± S.D.s of duplicate determinations from four (young) to eight (adult) independent experiments. Multiple comparisons showed DCNB Vmax values were significantly different between age groups by two-way ANOVA (P < 0.0001). In DCA-treated rats, there was a significant difference in CDNB Vmax between young males and adult females (P = 0.0126). The asterisks denote statistical significance when compared with the same kinetic parameter in acetate-treated controls: **P < 0.01; ***P < 0.001; ****P < 0.0001 (two-tailed Student’s t test).