The binding of deoxycorticosterone by the AtT-20 cell

The AtT-20 cell contains a steroid hormone binding site besides the glucocorticoid receptor. It binds 11-deoxycorticosterone (DOC) but not glucocorticoids, estrogens, mineralocorticoids, or progestins. Scatchard analyses could not quantitate the number of these sites, but suggested that there are many and that they have a low affinity for DOC. This new site is in the particulate fraction of the cell and at least part of the binding is associated with nuclei. The AtT-20 cell metabolizes DOC; up to 50% of the intracellular steroid is converted into a metabolite. Overall, although this new site could be involved in mediating antiglucocorticoid hormone action, its "low" binding affinity and location in the particulate fraction suggests that more likely it represents part of a hormone-metabolizing system.