GLUCOCORTICOID RECEPTOR COLOCALIZATION WITH PITUITARY-HORMONES IN THERAT PITUITARY-GLAND

The presence of glucocorticoid receptor (GR) in the anterior lobe of t he pituitary gland has previously been demonstrated, but the exact cel l types expressing GR have not yet been characterized. In this study, we demonstrate the colocalization of GR and pituitary hormones in the rat pituitary gland by using an immunocytochemical double-labelling me thod. The majority of anterior lobe corticotropin-immunoreactive and g rowth hormone-immunoreactive cells contained GR-like immunoreactivity. Cells of the intermediate lobe showed intensive ACTH-like immunoreact ivity but did not express GR. The glycoprotein hormones thyroid-stimul ating hormone, follicle-stimulating hormone and luteinizing hormone we re colocalized with GR to a lesser degree; approximately one-half of t he cells exhibiting immunoreactivity to these hormones contained GR. B y contrast, only a minority of the prolactin-immunoreactive cells expr essed GR. Our results suggest that glucocorticoids may differentially regulate the secretion and/or synthesis of these pituitary hormones by directly affecting the hormone-producing cells of the anterior pituit ary.