Effect of RU 38486 (a Potent Glucocorticoid Receptor Antagosist) on Insulin Receptor mRNA Levels in IM-9 Lymphocytes Cultured with or without Dexamethasone

Abstract

Glucocorticoid is known to increase insulin receptor mRNA, but it is unclear whether or not this effect is mediated through the glucocorticoid receptor.
In this study, by using RU 38486, which has a strong affinity for glucocorticoid receptors without exerting any glucocorticoid-like action, we investigated how dexamethasone affects insulin receptor mRNA levels in IM-9 cells.
The following results were obtained:
1) After 24 hours of culture, dexamethasone (10^-6M) significantly increased insulin receptor mRNA levels in IM-9 cells.
2) In a dose-dependent manner (10^-8-10^-10M), RU 38486 markedly inhibited the effects of dexamethasone (10^-6M) on insulin receptor mRNA levels.
3) There were no significant changes in insulin receptor mRNA levels in IM-9 cells cultured with RU 38486 (10^-8M) alone.
These results suggest that dexametasone increases insulin receptor mRNA after binding to its receptor at least in cultured IM-9 cells.