title: The role of ascorbic acid in the function of the adrenal cortex: studies in adrenocortical cells in culture.
abstract: To investigate the role of ascorbic acid in the function of the adrenal cortex, we studied the effects of ascorbate on the regulation of 11 beta-hydroxylase in culture. When primary bovine adrenocortical cells were cultured in a serum-free defined medium in the absence of ACTH, 11 beta-hydroxylase activity declined with a half-time of about 40 h. When 50 microM cortisol, which acts as a pseudosubstrate for 11 beta-hydroxylase, was added to such cultures, 11 beta-hydroxylase activity declined with a half-time of about 6 h. Ascorbate (5 mM) markedly reduced the rate of loss of 11 beta-hydroxylase activity in the presence of cortisol. Previous studies showed that phenolic and sulfoxide antioxidants, which also prevent loss of 11 beta-hydroxylase activity, inhibited the enzyme at concentrations somewhat higher than those required for protective activity. However, ascorbate at concentrations from 10 microM to 5 mM did not inhibit 11 beta-hydroxylase. The same range of ascorbate concentrations added to cells during a 24-h preincubation with cortisol showed increasing prevention of loss of 11 beta-hydroxylase activity. Ascorbate and a lowered concentration of oxygen were synergistic in their protective action. At 2% oxygen, 5 mM ascorbate almost completely prevented loss of 11 beta-hydroxylase activity in the presence of 50 microM cortisol. 11 beta-Hydroxylase activity was reinduced over a period of 5 days in third passage cultures by addition of 1 microM ACTH in defined lipoprotein-free medium. Addition of ascorbate enhanced the reinduction about 2-fold. The action of ascorbate in prevention of pseudosubstrate-mediated loss of activity and in enhancing reinduction of 11 beta-hydroxylase is specific; neither alpha-tocopherol nor selenium prevented loss of 11 beta-hydroxylase in the presence of cortisol or enhanced reinduction of 11 beta-hydroxylase in the presence of ACTH. As an additional test of specificity, it was shown that reinduction of 17-hydroxylase activity was completely unaffected by ascorbate, selenium, or alpha-tocopherol, and addition of cortisol to cultures with high 17-hydroxylase did not result in any loss of enzyme activity. Thus, a major function of ascorbate in the adrenal cortex is as a protective compound for cytochrome.
authors.forename: P J
authors.initials: PJ
authors.lastname: Hornsby
authors.forename: S E
authors.initials: SE
authors.lastname: Harris
authors.forename: K A
authors.initials: KA
authors.lastname: Aldern
mesh_terms: D000302:Adrenal Cortex / Q000187:drug effects / Q000502:physiology*; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology / Q000502:physiology*; D002417:Cattle; D002478:Cells, Cultured; D004790:Enzyme Induction; D006854:Hydrocortisone / Q000494:pharmacology; D010100:Oxygen; D012643:Selenium / Q000494:pharmacology; D013252:Steroid 11-beta-Hydroxylase / Q000096:biosynthesis; D013254:Steroid 17-alpha-Hydroxylase / Q000096:biosynthesis; D014810:Vitamin E / Q000494:pharmacology
chemical_list: D014810:Vitamin E; D000324:Adrenocorticotropic Hormone; D013254:Steroid 17-alpha-Hydroxylase; D013252:Steroid 11-beta-Hydroxylase; D012643:Selenium; D001205:Ascorbic Acid; D010100:Oxygen; D006854:Hydrocortisone