Interactions of indoles with specific binding sites for 2,3,7,8-tetrachlorodibenzo-p-dioxin in rat liver.
In order to identify some of the structural requirements for binding of indoles to the receptor for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), we have investigated the capacity of various indoles to inhibit specific [1,6-3H]TCDD binding in rat liver cytosol, as analyzed by electrofocusing in polyacrylamide gel. Of these indoles, indolo[3,2-b]carbazole was the most active. The IC50 value for receptor binding of indolo[3,2-b]carbazole as well as for 2,3,7,8-tetrachlorodibenzofuran was 3.6 nM, whereas that of 5,6-benzoflavone was 26 nM. Both indolo[3,2-b]carbazole and 2,3,7,8-tetrachlorodibenzofuran competitively inhibited the binding of [3H]TCDD to the receptor. The well-known microsomal enzyme inducer 3,3'-diindolymethane did not interact significantly with the TCDD receptor. Previous concepts of structure-activity relationships for binding of chlorinated dioxins to the TCDD receptor fail to account for the receptor binding of unhalogenated aryl hydrocarbon hydroxylase inducers such as 5,6-benzoflavone. We have instead considered the true three-dimensional space occupied by some receptor ligands by means of a computer using crystallographic data as inputs. When the atomic van der Waals radii were included, all potent receptor ligands studied could be fitted into a rectangle of 6.8 X 13.7 A.
D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis; D001667:Binding, Competitive; D003600:Cytosol / Q000378:metabolism; D004147:Dioxins / Q000378:metabolism*; D004790:Enzyme Induction / Q000187:drug effects; D007211:Indoles / Q000378:metabolism* / Q000494:pharmacology; D008099:Liver / Q000378:metabolism*; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology; D000072317:Polychlorinated Dibenzodioxins / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D018336:Receptors, Aryl Hydrocarbon; D011955:Receptors, Drug / Q000378:metabolism*; D013329:Structure-Activity Relationship
D004147:Dioxins; D007211:Indoles; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D011955:Receptors, Drug; D001189:Aryl Hydrocarbon Hydroxylases