Zinc(II) inhibits the release of thyroid and glucocorticoid receptors from chromatin of cultured GC cells

The effect of Zn(II) on the association of thyroid and glucocorticoid hormone receptors with chromatin was studied in chromatin from cultured GC cells. Chromatin was incubated at 0-4°C in 20 mM Tris, pH 7.4. When buffers contained 0.15 M NaCl, the release of T₃ receptors from chromatin was time-dependent; 50% of T₃ receptors were released after 30 min incubation. Receptor release appeared relatively specific since <10% of chromatin protein and DNA, and <13% of chromatin zinc were released under these conditions. Addition of Zn(II) inhibited receptor release; one-half maximal inhibition occurred at 1 μM ZnCl₂. Cd(II) and to a lesser extent (Co(II) had similar but smaller effects. Addition of EDTA prevented this effect of Zn(II); EDTA alone enhanced receptor release. Zn(II) also inhibited the release of glucocorticoid receptors from chromatin in similar incubations. Our findings suggest that Zn(II) increases the association of hormone receptors with chromatin and, thereby, may influence receptor function.