An approach to the mechanism of the potent antiglucocorticoid: 17 beta-hydroxy-11 beta-4-dimethylaminophenyl-17 alpha-propynyl-estra-4,9-dien-3-one

The effects of a new synthetic steroid, 17 beta-hydroxy-11 beta-4-dimethyl-aminophenyl-17 alpha-propynyl-estra-4,9-dien-3-one, classified under reference R38486 in the Roussel-Uclaf nomenclature [1], were investigated in two established rat hepatoma cell lines in order to gain information on the mechanism of action. The induction of tyrosine aminotransferase (TAT) and alanine aminotransferase (AAT) was totally abolished when R38486 was added with dexamethasone either on a 1-1 basis or on a 10-fold excess depending on the differentiation state of the cell. Binding studies showed a high affinity for the glucocorticoid receptor; however our "whole cell" study with [3H] R38486 indicates that only a low amount of antagonist-receptor complexes was translocated into the nucleus. Nuclear fractionation experiments showed that R38486, like the other antagonists studied, was located in the chromatin fraction where it may exert some definite role. Our observations based on whole cell experiments using physiological doses of glucocorticoid analogs indicate that the binding of activated antiglucocorticoid-receptor complexes to nuclear acceptor sites represents a physiologically significant process. Moreover the differences in the nuclear binding of antagonist-receptor- as compared to agonist-receptor-complexes may set off the machinery of antagonistic action.