Effects of glucocorticosteroids on prolactin and growth hormone production and characterization of the intracellular hormone receptors in rat pituitary tumour cells

Publisher Website
Google Scholar
Abstract
The effect of corticosterone and dexamethasone on the production of growth hormone and prolactin was studied in rat pituitary tumor cells (GH3-cells) in culture. Corticosterone and dexamethasone caused a dose-dependent stimulation of growth hormone synthesis, and the highest concentration (10-6 mol/l) increased growth hormone levels to 250% of controls. This concentration decreased prolactin synthesis to 25% of the control values. The cytosol fractions from monolayer cultures as well as from tumors of GH3-cells were found to possess receptor molecules for glucocorticoid hormones, having a sedimentation constant close to 8 S in a salt-free buffer and 4 S in the presence of 0.5 mol/l KCl. The isoelectric point of the receptor was 5.8. Scatchard analysis showed 1 single class of binding sites with high affinity (Kd 2.1 .+-. 0.4 (SD .times. 10-9 mol/l)). Studies on the steroid specificity revealed that dexamethasone had the highest affinity for the receptor. Corticosterone, cortisol and progesterone also had a high affinity, whereas testosterone and estradiol-17.beta. had no significant affinity for the receptors. After in vivo administration of [3H]dexamethasone to GH3 tumor-bearing rats, radioactivity could be extracted from purified nuclei bound to 4 S macromolecules. The presence of receptors for glucocorticosteroid hormones in the GH3-cells, suggests that these hormones may alter growth hormone and prolactin production at the anterior pituitary level.