Angiotensin-II acts via the type 1 receptor to inhibit 17 alpha-hydroxylase cytochrome P450 expression in ovine adrenocortical cells.
In this study we have investigated the effect of angiotensin-II (A-II) on cortisol production and 17 alpha-hydroxylase cytochrome P450 (P450(17 alpha)) expression in primary cultures of ovine adrenocortical cells and the A-II receptor subtypes that mediate these responses. While A-II alone had no stimulatory effect on cortisol secretion, it inhibited the cortisol response to ACTH (10(-8) M) in a dose-dependent manner (Ki, less than 0.1 nM; maximum inhibition, 60-80%). While prolonged treatment with ACTH (10(-8) M) increased the expression of P450(17 alpha), cotreatment with A-II (10(-8) M) also inhibited ACTH-stimulated expression, as determined by changes in mRNA, immunoreactive P450(17 alpha), and 17 alpha-hydroxylase activity. A study of the effects of the AT1 and AT2 receptor antagonists, DuP 753 and PD 123319, on binding of [125I]A-II to ovine adrenocortical cells showed that the A-II receptor population was predominantly of the AT1 subtype. The effects of A-II on inhibition of cortisol secretion in response to ACTH and the activation of phosphoinositidase-C in response to A-II alone were both fully antagonized by DuP 753, but not by PD 123319. Furthermore, the inhibitory effects of A-II on expression of P450(17 alpha), as measured at the levels of mRNA, immunoreactive protein, and enzyme activity, were reversed by DuP 753 (10(-5) M), but not PD 123319 (10(-5) M). We conclude that A-II has a potentially important role in the control of cortisol secretion and long term maintenance of P450(17 alpha) expression in the ovine adrenal cortex, and that the effects of A-II on both cortisol secretion and P450(17 alpha) expression are mediated through the AT1 receptor, which is coupled to phosphoinositidase-C.
Bird
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Cecil H. and Ida Green Center for Reproductive Biology Sciences, Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas 75235.
Magness
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Mason
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Rainey
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D000302:Adrenal Cortex / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D000324:Adrenocorticotropic Hormone / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000804:Angiotensin II / Q000378:metabolism / Q000494:pharmacology*; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D001713:Biphenyl Compounds / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D006854:Hydrocortisone / Q000378:metabolism*; D007093:Imidazoles / Q000494:pharmacology; D007700:Kinetics; D019808:Losartan; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D011945:Receptors, Angiotensin / Q000187:drug effects / Q000502:physiology*; D012756:Sheep; D013254:Steroid 17-alpha-Hydroxylase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D013777:Tetrazoles / Q000494:pharmacology; D015383:Zona Fasciculata / Q000201:enzymology; D015385:Zona Reticularis / Q000201:enzymology
D057911:Angiotensin Receptor Antagonists; D001713:Biphenyl Compounds; D007093:Imidazoles; D011725:Pyridines; D012333:RNA, Messenger; D011945:Receptors, Angiotensin; D013777:Tetrazoles; D000804:Angiotensin II; C073402:PD 123319; D000324:Adrenocorticotropic Hormone; D013254:Steroid 17-alpha-Hydroxylase; D010727:Phosphoric Diester Hydrolases; C021491:glycerophosphoinositol glycerophosphodiesterase; D019808:Losartan; D006854:Hydrocortisone