abstract
- The effects of various hormones were examined on the induction of heme oxygenase in monolayer cultures in chick embryo hepatocytes maintained in a chemically defined medium. Addition of insulin to the cultured cells markedly suppressed the activity of basal as well as Co2+-induced heme oxygenase. Treatment of cells with hydrocortisone also suppressed the basal enzyme activity, while the Co2+-induced enzyme activity was enhanced slightly. In contrast, triiodothyronine addition to the culture caused a slight increase of both uninduced and induced levels of the enzyme. This stimulatory effect of triiodothyronine was enhanced significantly by prolonged incubation of cells (48-96 hr) in the serum-free medium. These findings indicate that heme oxygenase synthesis can be substantially altered by changing the hormonal environment of the hepatocytes. Furthermore, the induction of heme oxygenase by Co2+ was inhibited by glucagon, dibutyryl cAMP and theophylline in a dose-dependent manner, suggesting that the enzyme induction may also be controlled by changes in cAMP levels.