The effect of molybdate on glucocorticoid receptor transformation and translocation in intact, viable AtT-20 mouse pituitary tumor cells

Abstract

The effect of 20 mM molybdate on the transformation and translocation of glucocorticoid receptors in intact AtT-20 mouse pituitary tumor cells was investigated. To test whether transformation of the receptor was inhibited during in vivo incubations with both molybdate and glucocorticoid, the DEAE cellulose elution profile of extracted receptor was determined. It was found that receptors from both high speed cytosols and nuclear extracts were transformed. To test whether translocation was affected by molybdate, the fraction of glucocorticoid-receptor complexes found in the nucleus was determined. At 37°C, in the absence of molybdate, 55–60%of the glucocorticoid receptor complexes were in the nuclear compartment. Molybdate did not effect the magnitude of nuclear translocation. Control studies suggested that the agent entered the cells, however. Cold exposure (0°C) reduced nuclear translocation to 20–25%. It is concluded that in vivo, either molybdate is not able to interact with the receptor or transformation in vivo is not mediated by the same molybdate-sensitive mechanisms currently being studied using broken cell-preparations.