Effects of luteolin on arylamine N-acetyltransferase activity in human liver tumour cells.

The human liver tumour cell line (J5) was selected in order to evaluate whether or not luteolin affected arylamine N-acetyltransferase (NAT) activity. Using high performance liquid chromatography, the NAT activity for acetylation of arylamine substrates (2-aminofluorene and p-aminobenzoic acid) was determined. The cytosolic NAT activity in human liver tumour cells was 2.74+/-0.26 and 1.68+/-0.20 nmol/min/mg of protein for 2-aminofluorene and p-aminobenzoic acid, respectively. Luteolin displayed a dose-dependent inhibition to cytosolic NAT activity and intact human liver tumour cells. Time-course experiments showed that NAT activity measured from intact human liver tumour cells was inhibited by luteolin for up to 24 h. Using standard steady-state kinetic analysis, it was shown that luteolin was a possible noncompetitive inhibitor to NAT activity in cytosols. This report is the first to show how luteolin affects NAT activity in human liver tumour cells.