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7,12-Dimethylbenz[a]anthracene (DMBA) is an adrenocorticolytic agent that causes apoplexy (haemorrhage) and massive necrosis in the adrenal cortex in rat. Several explanations regarding the origin of toxicity have been proposed. Huggins and Morii (J Exp Med 114:741-60, 1961) suggested that the cells of the inner adrenal cortex are the primary target, whereas Horváth and Kovács (Pathol Eur 8:43-59, 1973) suggested the vascular endothelium as being the origin of toxicity. In the present study, cultured precision-cut tissue slices were used to localize target cells for irreversible [(3)H]DMBA binding in rat and mouse adrenal cortex. The sites of binding were confirmed by autoradiography in vivo. Irreversible [(3)H]DMBA binding was confined to zona fasciculata/reticularis cells in rat (but not in mouse) adrenal cortex. Pronounced binding was observed in clusters of cells (focal binding), localized predominantly in zona reticularis of rat. [(3)H]DMBA binding in zona fasciculata/reticularis cells was inhibited by the cytochrome p450 1A/B (CYP1A/B) inhibitors ellipticine, alpha-naphthoflavone, and 1-ethynylpyrene. The CYP11B1-inhibitor metyrapone did not reduce [(3)H]DMBA binding. In CYP1-induced (PCB 126-treated) rats and mice, intense irreversible [(3)H]DMBA binding was found also in endothelial cells of the adrenal cortex. The endothelial binding was abolished by the CYP1 inhibitors but remained unaffected by metyrapone. We conclude that the metabolic activation in adrenal parenchymal cells is presumably catalysed by CYP1B1, whereas CYP1A1 presumably catalyses the activation in endothelial cells. We suggest that the adrenocorticolytic effect of DMBA is the result of a dual mode of action, targeting both endothelial and parenchymal cells in the rat adrenal cortex.
7,12-Dimethylbenz[a]anthracene (DMBA) is an adrenocorticolytic agent that causes apoplexy (haemorrhage) and massive necrosis in the adrenal cortex in rat. Several explanations regarding the origin of toxicity have been proposed. Huggins and Morii (J Exp Med 114:741-60, 1961) suggested that the cells of the inner adrenal cortex are the primary target, whereas Horváth and Kovács (Pathol Eur 8:43-59, 1973) suggested the vascular endothelium as being the origin of toxicity. In the present study, cultured precision-cut tissue slices were used to localize target cells for irreversible [(3)H]DMBA binding in rat and mouse adrenal cortex. The sites of binding were confirmed by autoradiography in vivo. Irreversible [(3)H]DMBA binding was confined to zona fasciculata/reticularis cells in rat (but not in mouse) adrenal cortex. Pronounced binding was observed in clusters of cells (focal binding), localized predominantly in zona reticularis of rat. [(3)H]DMBA binding in zona fasciculata/reticularis cells was inhibited by the cytochrome p450 1A/B (CYP1A/B) inhibitors ellipticine, alpha-naphthoflavone, and 1-ethynylpyrene. The CYP11B1-inhibitor metyrapone did not reduce [(3)H]DMBA binding. In CYP1-induced (PCB 126-treated) rats and mice, intense irreversible [(3)H]DMBA binding was found also in endothelial cells of the adrenal cortex. The endothelial binding was abolished by the CYP1 inhibitors but remained unaffected by metyrapone. We conclude that the metabolic activation in adrenal parenchymal cells is presumably catalysed by CYP1B1, whereas CYP1A1 presumably catalyses the activation in endothelial cells. We suggest that the adrenocorticolytic effect of DMBA is the result of a dual mode of action, targeting both endothelial and parenchymal cells in the rat adrenal cortex.
3-Methylsulfonyl-2,2'-bis(4-chlorophenyl)-1,1'-dichloroethene (MeSO(2)-DDE) is a potent, tissue-specific toxicant that induces necrosis of the adrenal zona fasciculata following a local CYP11B1-catalyzed activation to a reactive intermediate in mice. Autoradiography was used to examine CYP11B1-catalyzed binding of MeSO(2)-[(14)C]DDE and the adrenocorticolytic drug 2-(2-chlorophenyl)-2-(4-chlorophenyl)-1,1-dichlorethane; (o,p'-[(14)C]DDD, Mitotane, Lysodren) in human adrenal tissue slice culture. Both compounds gave rise to a selective binding in the one sample of normal adrenal zona fasciculata/reticularis, leaving zona glomerulosa and the adrenal medulla devoid of binding. Addition of the CYP11B1 selective inhibitor metyrapone (50 microM) reduced MeSO(2)-[(14)C]DDE binding below the detection limit, whereas o,p'-[(14)C]DDD binding was reduced only by 42%. Selective binding of MeSO(2)-[(14)C]DDE and o,p'-[(14)C]DDD was also observed in an aldosterone-producing adrenocortical carcinoma and in a nonfunctional adrenocortical hyperplasia. Exposure of slices from the normal adrenal cortex to MeSO(2)-DDE (25 microM) resulted in an increased accumulation of 11-deoxycorticosterone, 11-deoxycortisol and androstenedione in the medium, and exposure to o,p'-DDD (25 microM) did not alter the steroid secretion pattern. No histological changes were found in either MeSO(2)-DDE- or o,p'-DDD-exposed slices, compared with nonexposed slices. We suggest that MeSO(2)-DDE might act as a potent adrenocorticolytic agent in humans. Further studies are needed to establish the usefulness of MeSO(2)-DDE as a possible alternative for the treatment of adrenocortical hypersecretion and tumor growth.
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