Dexamethasone induces an increased biosynthesis of chromogranin A in rat pituitary gland

The influence of dexamethasone on the regulation of the biosynthesis of chromogranins A and B, two proteins originally described in adrenal chromaffin granules, was investigated in the rat pituitary gland. Dexamethasone increased chromogranin A levels and its corresponding mRNA in a dose-dependent manner. Induction of chromogranin A occurred with a time-lag of 24 h. As shown by immunohistochemistry, chromogranin A was present in control and dexamethasone-treated rats in gonadotrophic cells only. Chromogranin B, secretogranin II and the respective pituitary hormones co-stored with chromogranin A were not changed by dexamethasone. Thus dexamethasone selectively increased chromogranin A levels in gonadotrophic cells.