Chloroquine stabilizes hepatic glucocorticoid receptors.

Chloroquine (an antiarthritic, antimalarial, lysosomotropic amine) was found to significantly stabilize rat unbound hepatic glucocorticoid receptors in vitro for 2 h at 25 degrees C. Chloroquine stabilization was concentration dependent with statistically significant protection at 0.3 mM concentration and optimal effectiveness at approximately 3 mM. KC1 (0.3 M) induced unbound receptor inactivation at low temperature was also markedly reduced in the presence of 3 mM chloroquine. In addition, steroid prebound complexes were significantly stabilized at 4 degrees C and 25 degrees C by 3 mM chloroquine. Unlike molybdate (perhaps the most commonly used glucocorticoid receptor stabilizing reagent), chloroquine did not alter the sedimentation of glucocorticoid-receptor complexes in sucrose-density gradients. These results suggest that chloroquine may have useful application in glucocorticoid receptor quantitation, characterization and purification and may have interesting implications into the biological and pharmacological effects of chloroquine.