Effect of glucocorticoid levels in vivo on growth hormone biosynthesis

The rate of growth hormone (GH) biosynthesis in pituitary cells prepared from rats with different histories of glucocorticoid exposure was analyzed by a dual-labeling acrylamide-gel technique. Glucocorticoid deficiency, produced by adrenalectomy, reduces GH synthesis by approximately 50%. GH synthesis adrenalectomized rats treated with either natural or synthetic glucocorticoids, is restored to normal or above normal levels. Acute exposure (1 h) of cells to corticosterone in vitro does not produce a significant increase in GH synthesis. Adrenalectomized rats treated with steroid for one day show a small but detectable increase in GH synthesis, while treatment for 3--6 days results in progressively larger stimulatory effects. All of these results are similar to previous findings regarding glucocorticoid stimulation of GH synthesis in vitro.