The binding of deoxycorticosterone by the AtT-20 cell.

Area of Science:

• Endocrinology
• Cell Biology
• Molecular Pharmacology

Background:

• The AtT-20 cell line is a model for studying steroid hormone action.
• Glucocorticoid receptors are well-characterized in these cells.
• The existence of other steroid binding sites is less understood.

Purpose of the Study:

• To characterize a novel steroid hormone binding site in AtT-20 cells.
• To determine the binding specificity and characteristics of this new site.
• To investigate the potential role of this site in hormone action or metabolism.

Main Methods:

• Radioligand binding assays using 11-deoxycorticosterone (DOC).
• Scatchard analysis to assess binding affinity and capacity.
• Cellular fractionation to determine the subcellular localization of the binding site.
• Metabolic studies to investigate steroid transformation.

Main Results:

• A novel binding site in AtT-20 cells was identified that specifically binds 11-deoxycorticosterone (DOC).
• This site does not bind glucocorticoids, estrogens, mineralocorticoids, or progestins.
• Scatchard analysis indicated a high number of sites with low affinity for DOC.
• The binding site is located in the particulate fraction, with some association with nuclei.
• AtT-20 cells metabolize DOC, converting up to 50% into a metabolite.

Conclusions:

• AtT-20 cells possess a unique, low-affinity binding site for 11-deoxycorticosterone (DOC).
• The site's characteristics suggest it is likely involved in hormone metabolism rather than direct hormone action.
• Further research is needed to elucidate the precise function of this DOC-binding system.