Regulation of heme synthesis in HepG2 human hepatoma cells by dimethyl sulfoxide.

Dimethyl sulfoxide (DMSO) treatment of human HepG2 hepatoma cells increases the activity and the concentration of delta-aminolevulinic acid dehydratase (ALAD) to a comparable degree. Results of experiments with transcriptional inhibitors suggest that the increase in ALAD reflects de novo synthesis of the enzyme resulting from transcriptional activation. Commitment to increased ALAD activity in HepG2 cells is seen after 18 hr and complete by 48 hr. In contrast to the effects on ALAD, DMSO decreases the activities of porphobilinogen deaminase and uroporphyrinogen decarboxylase.