Stable expression of rat sulfotransferase 1B1 in V79 cells: Activation of benzylic alcohols to mutagens

Abstract

We have constructed Chinese hamster V79-derived cell lines (V79-rSULT1B1-A and -B) that express rat sulfotransferase 1B1 (rSULT1B1). Sulfotransferase activity towards 1-naphthol was 1020 ± 220 pmol/min/mg cytosolic protein in V79-rSULT1B1-A cells and 57 ± 9 pmol/min/mg in V79-rSULT1B1-B cells. These activities were similar over 100 population doublings and at varying cell densities. Immunostaining indicated a cytoplasmatic localization of rSULT1B1. Expression usually was homogeneous within colonies but showed some variation between colonies. The level of rSULT1B1 protein in V79-rSULT1B1-B cells was similar to that in rat liver but higher than in colon mucosa. The cytotoxicity of the benzylic alcohols 4H-cyclopenta[def]chrysen-4-ol and 6-hydroxymethylbenzo-[a]pyrene was enhanced >100-fold in V79-rSULT1B1-A cells compared with SULT-deficient cells (V79p). Likewise, these compounds showed mutagenic effects (at the hprt locus) in V79-rSULT1B1-A cells starting at a concentration of 0.02 and 0.01 μM, respectively, but were inactive in V79p cells even at a concentration of 1 μM. The cell line with the lower expression level, V79-rSULT1B1-B, showed only marginal toxification of the compounds investigated, indicating an important role of the expression level in the test system. A thoroughly characterized mammalian cell system, including positive controls, is now available for studying rSULT1B1-mediated bioactivation of promutagens; and protoxicants.