Transient stabilization of cholecystokinin A receptor mRNA by glucocorticoids in pancreatic AR42J cells.

We have characterized the effects of glucocorticoids on gene expression of the cholecystokinin A receptor (CCK-R) using a cloned cDNA probe in the rat pancreatic acinar cell line AR42J. Dexamethasone (100 nM) resulted in a transient, time-dependent increase of CCK-R mRNA, with a maximal induction observed after 3 h of hormone treatment (238 +/- 29% of controls, n = 4). Further incubation with dexamethasone resulted in a subsequent decrease of CCK-R mRNA concentrations, which reached control values after 12 h of hormonal treatment. The increase of CCK-R mRNA was dose dependent with half-maximal effects observed at 10 nM and maximal effects observed at 100 nM of hormone. We next investigated the molecular mechanisms by which glucocorticoids induce CCK-R gene expression. Nuclear run-on analysis revealed that dexamethasone pretreatment had no significant effect on CCK-R gene transcription. Using actinomycin D, we determined the half-life for the mRNA of the CCK-R. Dexamethasone (100 nM) pretreatment for 3 h resulted in a significant increase of CCK-R mRNA stability, with a half-life of 240 min compared with 120 min in untreated control cells. These data therefore suggest that glucocorticoids transiently stimulate CCK-R mRNA concentrations by increasing the mRNA stability without affecting the receptor transcription rate.