Influence of culture system and medium enrichment on sulfotransferase and sulfatase expression in male rat hepatocyte cultures

The expression of sulfotransferase and steroid sulfatase was studied in rat liver using the most promising culture models of hepatocytes, including mo nolayer culture with a pyruvate (30 mM) enriched medium, co-culture with ra t epithelial cells from primitive biliary origin and collagengel sandwich c ulture. In the latter, addition of dexamethasone (1 muM) to the medium was examined. Phenol sulfotransferase enzymes (SULT1) were studied by measuring activities towards I -methylphenol and estradiol, hydroxysteroid sulfotran sferase (SULT2A) activity was determined towards dehydroepiandrosterone (DH EA). Microsomal steroid sulfatase activity was measured towards estrone sul fate, Western blot analysis was carried out using polyclonal antibodies rai sed against rat phenol sulfotransferase SULT1A1 (ASTTV), estrogen sulfotran sferase SULT1E1 (EST) and hydroxysteroid sulfotransferase (HST). SULT2A act ivity towards DHEA was maintained at a high level during the whole culture time. In the co-culture it even reached the level of freshly isolated cells . Addition of pyruvate had no positive effect on the activity measured in m onolayer cultures. High SULT1A1 activity towards 4-methylphenol was found i n the co-culture system. In the monolayer culture, the activity initially d ecreased with 35% but was then kept at a constant level, while in the sandw ich culture low activities were measured. For dexamethasone, an inducing ef fect on the various SULT activities could not be detected. Independently of the culture model used, the SULT1E1 activity towards estradiol decreased t o 20% and 5% of the initial activity after four and seven days of culture, respectively. Microsomal steroid sulfatase activity was best maintained in collagengel sandwich cultures. During the first four days in culture it ret ained 73% of the initial activity, afterwards it decreased to 40% of the ac tivity found in freshly isolated hepatocytes, irrespective of the culture c onditions. High expectations exist for collagengel sandwich cultures, howev er, in our study the results were rather disappointing. Monolayer is a suit able culture model for short-term purposes. For long-term in vitro biotrans formation studies, co-culture is preferred but is rather complex. (C) 2001 Elsevier Science Inc. All rights reserved.