Interaction of glucocorticoid receptors from lymphoid cell lines with their nuclear acceptor sites

Procedures have been developed which provide simple means of determining binding constants of steroid receptors for glucocorticoids in mouse lymphoid cell lines and of characterizing the interaction of the steroid--receptor complex with the nucleus. An average of 70% of the steroid--receptor complexes is found associated with the nuclear fraction in three investigated cell lines, whereas 30% of the steroid--receptor complexes is found in the cytosol fraction. This distribution of the steroid-receptor complex within the cell is independent of whether steroid uptake of the cells is performed at low or at high steroid concentration. Part of the binding of the steroid receptor to the nuclear fraction is sensitive to high ionic strength and to high pH. A larger fraction of the steroid--receptor complex binding to the nuclear fraction is insensitive to high ionic strength and pH when the steroid uptake is performed at low steroid concentrations than when performed at high steroid concentrations. Steroid--receptor complex is released from the nuclear fraction by DNAase treatment but not by RNAase treatment. The possible correlation between the sensitivity to ionic strength and pH and the specificity of the binding is discussed.