<p>Persistent environmental pollutants were examined for their interaction with the glucocorticoid hormone system. The focus was placed on interference with the glucocorticoid synthesis and the glucocorticoid-signalling pathway in various <i>in vitro</i> test systems.</p><p>Several aryl methyl sulphones competitively inhibited CYP11B1 activity in mouse adrenocortical Y1 cells. The DDT metabolite, 3-methylsulphonyl-2,2’-bis(4-chlorophenyl)-1,1’-dichloroethene (3-MeSO₂-DDE) had a higher affinity to the enzyme than the endogenous substrate, 11-deoxycorticosterone. In fact, 3-MeSO₂-DDE (K_i 1.6 μM) was almost as potent as the drug metyrapone (K_i 0.8 μM), a well-known inhibitor of the enzyme. 3-MeSO₂-DDE inhibited CYP11B1 activity in human adrenocortical H295R carcinoma cells, and at higher concentrations the CYP21 activity. The human H295R cell line seems to be a useful test system for studies of enzyme activities and could be used to screen endocrine disrupting chemicals interfering with the glucocorticoid hormone synthesis.</p><p>Several chiral PCB methyl sulphones and the fungicide tolylfluanid proved to be antagonists to the glucocorticoid receptor (GR) in rat hepatoma cells and/or Chinese hamster ovary cells stable transformed with a human GR and a responsive reporter vector. The 4-methylsulphonyl-2,3,6,2’,4’,5’-hexachlorobiphenyl (4-MeSO₂-CB149) enantiomers had similar antagonistic effect on the GR. Co-exposure of substances led to additive inhibitory effects on glucocorticoid-regulated protein synthesis in rat hepatoma cells. In general, 4-substituted but not 3-substituted methylsulphonyl-PCBs interacted with the glucocorticoid hormone system.</p><p>In the environment, humans and wildlife are constantly exposed to a wide range of chemicals. Considering the effects of these substances via mechanisms of actions described in this thesis, interference of xenobiotics with the glucocorticoid hormone system deserves further attention. In conclusion, environmental pollutants can interact with the glucocorticoid hormone system <i>in vitro</i>, yet the effects of the tested substances on this hormone system remain to be established <i>in vivo.</i></p>

Persistent environmental pollutants were examined for their interaction with the glucocorticoid hormone system. The focus was placed on interference with the glucocorticoid synthesis and the glucocorticoid-signalling pathway in various in vitro test systems. Several aryl methyl sulphones competitively inhibited CYP11B1 activity in mouse adrenocortical Y1 cells. The DDT metabolite, 3-methylsulphonyl-2,2’-bis(4-chlorophenyl)-1,1’-dichloroethene (3-MeSO2-DDE) had a higher affinity to the enzyme than the endogenous substrate, 11-deoxycorticosterone. In fact, 3-MeSO2-DDE (Ki 1.6 μM) was almost as potent as the drug metyrapone (Ki 0.8 μM), a well-known inhibitor of the enzyme. 3-MeSO2-DDE inhibited CYP11B1 activity in human adrenocortical H295R carcinoma cells, and at higher concentrations the CYP21 activity. The human H295R cell line seems to be a useful test system for studies of enzyme activities and could be used to screen endocrine disrupting chemicals interfering with the glucocorticoid hormone synthesis. Several chiral PCB methyl sulphones and the fungicide tolylfluanid proved to be antagonists to the glucocorticoid receptor (GR) in rat hepatoma cells and/or Chinese hamster ovary cells stable transformed with a human GR and a responsive reporter vector. The 4-methylsulphonyl-2,3,6,2’,4’,5’-hexachlorobiphenyl (4-MeSO2-CB149) enantiomers had similar antagonistic effect on the GR. Co-exposure of substances led to additive inhibitory effects on glucocorticoid-regulated protein synthesis in rat hepatoma cells. In general, 4-substituted but not 3-substituted methylsulphonyl-PCBs interacted with the glucocorticoid hormone system. In the environment, humans and wildlife are constantly exposed to a wide range of chemicals. Considering the effects of these substances via mechanisms of actions described in this thesis, interference of xenobiotics with the glucocorticoid hormone system deserves further attention. In conclusion, environmental pollutants can interact with the glucocorticoid hormone system in vitro, yet the effects of the tested substances on this hormone system remain to be established in vivo.

The DDT metabolite 3-methylsulphonyl-DDE (3-MeSO2-DDE) induces cell death specifically in the adrenal cortex of mice after a cytochrome P45011B1 (CYP11B1)-catalysed bioactivation. This substance is not only an environmental pollutant, but also a suggested lead compound for an improved chemotherapy of adrenocortical carcinoma (ACC). The aim of the thesis was to further investigate this compound in terms of kinetics, cell death mechanisms and species differences. The pharmacokinetics of 3-MeSO2-DDE and the current drug for ACC, o,p’-DDD, was studied during 6 months following a single dose in minipigs. The elimination was slower for 3-MeSO2-DDE than for o,p’-DDD, indicated by a lower clearance and longer t½ in plasma and subcutaneous fat. Both substances remained in fat tissue during the whole study period. Unlike o,p’-DDD, 3-MeSO2-DDE was retained also in liver. The adequacy of the murine adrenocortical cell line Y-1 was evaluated for studies of adrenotoxic compounds. The Y-1 cells proved to be an appropriate test system for future mechanism studies, since CYP-catalysed irreversible binding, inhibited corticosterone production induced by 3-MeSO2-DDE and o,p’-DDD were successfully demonstrated. Cell death of 3-MeSO2-DDE in the mouse adrenal cortex was implied to be necrotic. Early apoptotic signalling (i.e. up-regulation of caspase-9) was observed, although it seemed to be interrupted by ATP-depletion and anti-apoptotic actions by heat shock protein 70, resulting in lack of activation of caspase-3. Using cultured adrenal tissue slices, two not previously studied species were examined ex vivo regarding adrenal binding of 3-MeSO2-[14C]DDE. Binding was found in the hamster adrenal cortex and in assumed cortical cells in the medulla, while the guinea pig adrenal was devoid of binding. This emphasises the species specificity in bioactivation of 3-MeSO2-DDE. The thesis forms a basis for further investigations in the human adrenocortical cell line H295R and provides new knowledge of importance for toxicological risk assessment of 3-MeSO2-DDE.