Activation and deactivation of the glucocorticoid hormone-receptor complex.

Cytosol glucocorticoid receptors acquired the ability to bind to DNA-cellulose on incubation at 25–37°C and/or in media of high ionic strength (0.3 M K Cl). However, this activation was transient only. It was followed by deactivation whose rate was also dependent on incubation temperature and on the presence of potassium chloride. Deactivation resulted in a decreased but non-zero binding to DNA-cellulose. Specific triamcinolone acetonide binding to the receptor protein was not lost under the same conditions. Deactivation commenced before it became apparent, probably together with activation. Preactivated complex underwent deactivation even in conditions that would not allow significant decrease in DNA-cellulose binding without previous incubation at 37°C. In contrast to previous reports it was found that fast activation/deactivation took place in the presence of 4 mM Ca2+. Molybdate ions slow down both activation and deactivation, but do not prevent activation by heat. Heat activated/deactivated complex differed in size from both non-activated and Ca2+-deactivated complexes. This finding suggests that heat and Ca2+-induced deactivation follow different mechanisms.