Corticotropin-releasing factor and forskolin increase proopiomelanocortin messenger RNA levels in rat anterior and intermediate cells in vitro.

The effect of ovine corticotropin-releasing factor (CRF) on messenger ribonucleic acid (mRNA) level encoding proopiomelanocortin (POMC) was studied in serum-free primary cultures of intermediate (IL) and anterior lobe (AL) cells of rat pituitary. Levels of POMC mRNA were quantitated by hybridization to a 32P-labeled, single-stranded POMC complementary deoxyribonucleic acid (cDNA) probe. This effect was time dependent and after 48 h of treatment, POMC mRNA levels in IL cells and AL corticotrophs were increased by 116 +/- 9% and 118 +/- 2% of control values, respectively. Forskolin (1 microM) induced a similar increase in POMC mRNA in both pituitary cell types. These data suggest that CRF might stimulate the gene expression of POMC in pituitary melanotrope and corticotrope cells. Moreover, our findings are consistent with the role of cAMP as a second messenger for CRF in IL and AL corticotrophic cells.