Endocrine Abstracts

The capacity of the adrenal to produce cortisol is controlled in part by the transcription of 21 hydroxylase(CYP21) and production of androgens by 17 hydroxylase/17-20 lyase(CYP17) in response to secretogoues including ACTH, angiotensin-II(A-II) and forskolin. Both mRNA and protein expression of CYP21 was upregulated in the presence of forskolin and A-II alone and in combination in vitro H-295 adrenocortical cells, as detected by northern and western blotting. Whereas, mRNA expression of CYP17 was up-regulated in the presence of forskolin and insulin. CYP17 protein expression was found to be increased in the presence of insulin and A-II. Response elements for the orphan nuclear receptor SF-1 and nur-77 were identified on the promoter region of CYP17 and CYP21. The ability of SF-1 and nur-77 to regulate transcription of these enzymes was examined. SF-1 was expressed throughout the adrenal cortex and was localised predominantly to the nucleus. Forskolin, A-II and insulin increased the protein expression and nuclear translocation of SF-1. Using mobility shift assays increased binding of SF-1 to its response element in the presence of forskolin, A-II and insulin but not A-II in combination with forskolin was observed. Nur-77 was expressed primarily in the zona fasciculata. Increased protein expression of nur-77 and the greatest binding of nur-77 to its response element was seen when cells were stimulated with A-II in combination with forskolin. Insulin had no effect on protein expression or activity of nur-77. These data indicate that nur-77 may regulate steroid enzyme genes relevant to cortisol production and thereby regulate differential cortisol and adrenal androgen production.