Adrenalectomy enhances the induction of heme oxygenase and the degradation of cytochrome P-450 in liver.

Overview

The induction of hepatic heme oxygenase in response to cobaltous chloride (CoCl2) administration was examined in normal, sham-operated, and adrenalectomized rats. The basal level of heme oxygenase was elevated about 2-fold in adrenalectomized rats as compared to normal controls or sham-operated animals. The extent of heme oxygenase induction by CoCl2 was also increased about 2-fold above normal in adrenalectomized animals and was accompanied by an enhanced breakdown of cytochrome P-450. The initial decline (approximately 2 h) and the late rebound increase (approximately 16 h) of delta-aminolevulinate synthase activity caused by the metal administration were, however, similar for all three groups of animals. Hydrocortisone is known to restore the impaired inducibility of delta-aminolevulinate synthase by allylisopropylacetamide in adrenalectomized rats. In this study, treatment with hydrocortisone prevented the exaggerated metal induction of heme oxygenase but did not affect the associated initial decline or the late rebound of delta-aminolevulinate synthase. These data indicate that hydrocortisone and adrenalectomy can significantly influence the extent of the induction of heme oxygenase produced by CoCl2, but that both the initial decline and the rebound induction of delta-aminolevulinate synthase associated with this metal treatment are apparently independent of these endocrine controls.