Hep G2 cell line as a human model for sulphate conjugation of drugs.

1. The objective of this study was to examine the usefulness of the hepatoma cell line Hep G2 as a model for human sulphoconjugation of drugs, in particular stereoselective conjugation. 2. Using the substrates p-nitrophenol and dopamine, we found sulphation activities consistent with the presence of both the phenol (P) and the monoamine (M) form of the human phenolsulphotransferases in these cells. 3. The Kmapp was 3.0 microM for the sulphation of p-nitrophenol. This activity was inhibited selectively by 2,6-dichloro-4-nitrophenol, IC50 6 microM. The Kmapp was 39 microM for the sulphation of dopamine. This activity was selectively inhibited by elevated temperature. 4. The chiral adrenergic drugs (+/-)-terbutaline and (+/-)-4-hydroxypropranolol were both sulphated stereoselectively with Kmapp and Vmaxapp values for each enantiomer virtually identical to previous observations with human liver cytosol. 5. In a direct comparison, the estimated activity of the P form of phenolsulphotransferase in the Hep G2 cell line was 30% of that in human liver, whereas, surprisingly, the activity of the M form of phenolsulphotransferase was 4.5 times higher in the Hep G2 cells than in the liver.