Annexin-1 (lipocortin-1)-immunoreactivity in the folliculo-stellate cells of rat anterior pituitary: the effect of adrenalectomy and corticosterone treatment on its subcellular distribution

In the pituitary gland, annexin-1 (lipocortin-1) located in folliculo-stellate (FS) cells has been advocated as one of the candidates for paracrine agents produced by FS cells that modulate the release of pituitary hormones. However, the expression and distribution pattern of annexin-1 in FS cells under different circulating corticosteroid conditions has not been examined. Thus, by means of pre-embedding immunoelectron microscopy, we investigated the expression of annexin-1 in FS cells under different corticosteroid conditions. Annexin-1-immunoreactivity was observed in the cytoplasm; especially intense immunoreactivity was detected in the follicle surface of FS cells under control conditions. After adrenalectomy, annexin-1-immunoreactivity almost disappeared, but the immunoreactivity recovered with corticosterone replacement. The expression of glucocorticoid receptor immunoreactivity in the nucleus of FS cells also showed a similar pattern to annexin-1 associated with the changes in the corticosteroid conditions. However, S-100 immunoreactivity, a marker for FS cells, was not changed whatever the corticosteroid conditions. These results confirm that glucocorticoids regulate the annexin-1 expression and demonstrate the translocation of annexin-1 from intracellular to pericellular sites in the FS cells of the rat anterior pituitary gland.

Intracellular dynamics of steroid hormone receptor

Steroid hormones substantially influence brain development, reproduction sexual differentiation and emotion. These effects are mediated by steroid hormone receptors and cofactors, which directly regulate gene expression. Deciphering how and where these transcriptional activators occur in a cell provides the groundwork for elucidating the influence of these small hydrophobic signal molecules on various brain functions. This paper describes some of the recent investigations into the subcellular localization of steroid hormone receptors and cofactors using GFPs and other immunocytochemical methods.

Cellular localization and distribution of glucocorticoid receptor immunoreactivity and the expression of glucocorticoid receptor messenger RNA in rat pituitary gland. A combined double immunohistochemistry study and in situ hybridization histochemical analysis

By means of double immunohistochemical techniques and a nonradioisotopic in situ hybridization method, we determined the colocalization pattern of glucocorticoid receptor (GR) and pituitary hormones and the GR messenger RNA (mRNA) expression in the pituitaries of Wistar adult male rats. Immunoreactivity for GR was detected in the nuclei of cells in the anterior and posterior pituitary. Double immunohistochemistry revealed that the colocalization of GR and anterior pituitary hormones occurred in almost 99% of the growth hormone (GH)-producing cells and adrenocorticotropic hormone (ACTH)-producing cells, and in 67% of the thyroid stimulating hormone (TSH)-producing cells. Almost all of the folliculostellate cells (93%), marginal layer cells (94%) in the anterior pituitary, and pituicytes (96%) in the posterior pituitary immunostained for S100 protein antibody were also immunostained with GR. GR mRNA was abundant in the cytoplasm of anterior and intermediate pituitary cells but scattered sparsely in that of the posterior pituitary. These results suggest that glucocorticoids directly influence certain pituitary cells in order to regulate cell function, including the synthesis and/or secretion of hormones.