Glucocorticoids enhance the cholesterol side-chain cleavage activity of ovine adrenocortical mitochondria.
We have shown previously that a chronic treatment with glucocorticoids enhances cAMP- or ACTH-induced steroidogenesis of cultured ovine adrenocortical cells. This effect appears to involve a greater amount of cholesterol in mitochondria. Hence, the present study aimed to define the role of glucocorticoids in cholesterol metabolism by these cells. 2-day-old cultures were exposed to different hormones or inhibitors (10(-6) M ACTH, 10(-5) M metyrapone) for 28-48 h. At the end of the treatment period, the cells were stimulated for 2 h with 10(-3) M 8Br-cAMP, in the presence of 10(-3) M aminoglutethimide (in order to load mitochondria with cholesterol). Mitochondria were then isolated and incubated without or with 100 microM cholesterol either in the presence or absence of 10(-3) M CaCl2, or with 25 microM 22R-hydroxycholesterol. Mitochondria isolated from dexamethasone-treated cells produced consistently more pregnenolone than mitochondria from control cells, suggesting that at least part of the additional cholesterol present in these mitochondria was available for steroidogenesis. However, similar differences were obtained when mitochondria were incubated in the presence of exogenous cholesterol, both with or without calcium, or in the presence of 22R-hydroxycholesterol. Pregnenolone production under these latter conditions was much higher than when endogenous cholesterol was the only substrate. Conversely, metyrapone treatment of the cells resulted in lower production of pregnenolone from 22R-hydroxycholesterol by their mitochondria. Likewise ACTH treatment enhanced pregnenolone production by isolated mitochondria irrespective of the incubation conditions. These effects of dexamethasone and ACTH were not related to higher amounts of adrenodoxin, adrenodoxin reductase or cytochrome P450scc. These results indicate that exposure of ovine adrenocortical cells to glucocorticoids or ACTH enhances their steroidogenic potency not only by increasing the amount of cholesterol available for steroidogenesis but also by enhancing some step(s) involved in the transformation of cholesterol into pregnenolone.
Picard-Hagen
N
N
INRA PRMD, 37380 Nouzilly, Lyon, France.
Darbeida
H
H
Durand
P
P
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000302:Adrenal Cortex / Q000166:cytology / Q000378:metabolism*; D000305:Adrenal Cortex Hormones / Q000096:biosynthesis; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000325:Adrenodoxin / Q000096:biosynthesis; D000616:Aminoglutethimide / Q000494:pharmacology; D000818:Animals; D002122:Calcium Chloride / Q000494:pharmacology; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism* / Q000494:pharmacology; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005287:Ferredoxin-NADP Reductase / Q000096:biosynthesis; D005938:Glucocorticoids / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D006888:Hydroxycholesterols / Q000378:metabolism / Q000494:pharmacology; D008797:Metyrapone / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D011284:Pregnenolone / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D012756:Sheep; D013256:Steroids / Q000494:pharmacology
D000305:Adrenal Cortex Hormones; D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D005938:Glucocorticoids; D006888:Hydroxycholesterols; D012333:RNA, Messenger; D013256:Steroids; D000616:Aminoglutethimide; D000325:Adrenodoxin; C003585:22-hydroxycholesterol; D015124:8-Bromo Cyclic Adenosine Monophosphate; D011284:Pregnenolone; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D003577:Cytochrome P-450 Enzyme System; D002784:Cholesterol; D005287:Ferredoxin-NADP Reductase; D002122:Calcium Chloride; D008797:Metyrapone