Physiological action and receptor binding of a newly synthesized and novel antiglucocorticoid.

RU 38486, a newly synthesized molecule, reversed glucocorticoid mediated enzyme induction and gluconeogenesis in the liver, and RNA synthesis in rat thymocytes. The transfer of radiolabelled dexamethasone from the cytoplasm to the nucleus was also opposed by RU 38486 in intact thymocytes. Although RU 38486 saturated the same molecular species of the receptor as the hormone in the liver, differences seemed to appear when thymus was taken into account. Along with the ongoing clinical trials, an important new tool thus appears at hand to understand and harness the molecular action of glucocorticoid hormones in mammalian systems.