Schimchowitsch S, Plante M, Kienlen P, Félix J M, Koch B, Stoeckel M E
CNRS URA 1446, Neurophysiologie et Neurobiologie des Systèmes Endocrines, Strasbourg, France.
J Neuroendocrinol. 1994 Aug;6(4):385-90. doi: 10.1111/j.1365-2826.1994.tb00597.x.
The leporidae (rabbit and hare) pituitary intermediate lobe (IL) differs from that of other mammals by its neuroendocrine regulation. In particular, it is not submitted to the classic dopaminergic inhibitory control, which has been considered as a repressive factor for the expression of glucocorticoid receptors (GR) in the mammalian IL. Hence, the present experiments aimed at examining the rabbit IL for the possible existence of GR. Using both immunocytochemistry and binding studies with (3H)-dexamethasone, we localized GR in the nuclei of IL cells and showed the presence of saturable and high-affinity type II receptor sites, with Kd approximately 3.9 nM. Also, exposure of cultured IL cells to 10 nM dexamethasone (DEX) resulted in the blockade of melanocyte-stimulating hormone (alpha MSH) secretion stimulated by oxytocin (OT). Importantly, the inhibitory effect was reversed by a 100-fold excess of the glucocorticoid antagonist RU 38486. This is the first study which clearly demonstrates in a mammalian IL, namely the rabbit, the presence of functional GR, involved in the negative regulation of the melanotrophic activity of this gland.
兔科动物（兔和野兔）的垂体中间叶（IL）在神经内分泌调节方面与其他哺乳动物不同。特别是，它不受经典多巴胺能抑制控制，而这种控制被认为是哺乳动物IL中糖皮质激素受体（GR）表达的抑制因子。因此，本实验旨在检测兔IL中是否可能存在GR。通过免疫细胞化学和用（3H）-地塞米松进行结合研究，我们将GR定位在IL细胞的细胞核中，并显示存在可饱和的高亲和力II型受体位点，解离常数（Kd）约为3.9 nM。此外，将培养的IL细胞暴露于10 nM地塞米松（DEX）会导致催产素（OT）刺激的促黑素细胞激素（α-MSH）分泌受阻。重要的是，糖皮质激素拮抗剂RU 38486过量100倍可逆转这种抑制作用。这是第一项明确证明在哺乳动物IL（即兔）中存在功能性GR的研究，该GR参与了该腺体黑素营养活性的负调节。
