Manipulation of the phenotype of immortalised rat hepatocytes by differentculture configurations and by dimethyl sulphoxide

The liver-specific phenotype of immortalised rat hepatocytes is not irretri evably lost as they age in culture but can be manipulated by modifying the culture environment. Testosterone metabolism was used to investigate the profile of cytochrome P 450 isoenzymes present in two immortalised cell lines, P9 and LQC, and in p rimary cultures of rat hepatocytes, cultured on collagen films, gels and do uble gel cultures (sandwich configuration). The extent of testosterone meta bolism, and the range of metabolites produced, was increased in immortalise d cells by the presence of collagen as a substratum film or gel but surviva l was poorer and the range of metabolites was reduced in sandwich culture. In contrast, testosterone metabolism was retained in primary hepatocytes in sandwich cultures at a higher level than in collagen film or gel cultures. Expression of alpha class glutathione-S-transferases (GSTs) increased and t hat of GSTP1 decreased (changes which indicate a recovery of normal liver G ST phenotype) when the medium of immortalised cell cultures was supplemente d with dimethyl sulphoxide (DMSO). DMSO also improved ethoxyresorufin O-dee thylation (EROD) and testosterone metabolism in immortalised cells. It also markedly inhibited proliferation, DNA, RNA and protein synthesis. Maximal testosterone metabolism was observed in immortalised cells cultured on collagen gels in the presence of 1% (v/v) DMSO. Development of a protoc ol for treating immortalised liver cells cultured on collagen gels with DMS O to switch between proliferation and differentiation may provide a conveni ent system expressing the xenobiotic metabolising enzymes required for in v itro toxicity testing.