- 學位論文
泌乳素在腎上腺類固醇生合成的直接效果與機制
Direct Effect of Prolactin on Adrenal Steroidogenesis and It's Mechanism
摘要
泌乳素(Prolactin, PRL)由198個胺基酸所構成的內泌素，為腦垂腺前葉泌乳素分泌細胞(Lactotrophs)所分泌。正常的生理值下，泌乳素在調節乳腺發育、泌乳與卵巢功能上扮演重要的角色。高泌乳素血症(Hyperprolactinemia, HPRL)發生原因常為腦垂腺腺瘤，導致大量泌乳素存在於血液中，除引起女性月經失調、溢乳或不孕，也易導致腎上腺功能過高等症狀。腎上腺皮質是體內類固醇內泌素首要的合成器官，分泌類固醇的種類為醣皮質醇(Glucocorticoid)、鹽皮質醇(Mineralocorticoid)、性類固醇(Sex hormone)等三類，維持許多生理功能的運作如醣類、水分與電解質之平衡。腎上腺皮質細胞表現泌乳素受體的發現，暗示泌乳素可能直接影響腎上腺皮質細胞類固醇生成，也提供了高泌乳素血症引發腎上腺功能過高症狀的解釋。本實驗的目的在了解泌乳素對腎上腺類固醇生合成的直接作用及其機制。 以人類腎上腺皮質細胞株(NCI-H295)作為試驗模式，收集以PRL藥物處理後之細胞培養液，以酵素免疫分析法發現，PRL在極短的時間內即可以增加孕酮(Progesterone, P4)和皮質醇(cortisol, F)的分泌，因此PRL必參與急性調節的作用。以西方點墨法(Western blotting)與反轉錄聚合酶鏈反應(Reverse Transcription-PCR, RT-PCR)偵測，分別發現PRL能夠有效增加P450scc蛋白質表現以及StAR mRNA表現。 使用JAK2抑制劑AG490 、MEK/ERK1/2抑制劑U0126、PKA抑制劑H89，皆有效阻止PRL對類固醇生成的急性調節作用。此外，JAK2與PKA抑制劑能減弱PRL對P450scc表現的慢性刺激作用，但是三者皆能抑制PRL對類固醇生成的刺激作用。顯然，PRL經由JAK2與PKA傳訊途徑調節P450scc表現，但是經由MEK/ERK1/2傳訊途徑調節不明因子，而刺激腎上腺皮質類固醇的生成。
並列摘要
Prolactin (PRL) is a 23 kDa protein hormone closely related to growth hormone. It is secreted by lactotrophs in the anterior pituitary and primarily functions to enhance breast development during pregnancy and to induce lactation. Hyperprolactinemia, a condition of abnormal elevation in the serum PRL level caused by differential physiologic conditions, is frequently associated with hirsutism, hypogonadism, and amenorrhea due to anomalous adrenal and gonadal functions. Since the expression of PRL receptor has been detected by immunohistochemistry and RT-PCR in the human adrenal glands, it is speculated that PRL has a direct effect on adrenals. In this study, we want to investigate the function of PRL on adrenal steroid biosynthesis and its mechanism. We used the human adrenocortical NCI-H295 cell line as the model. After treated with PRL, the culture medium was collected and detected by ELISA. The administration of PRL stimulated progesterone (P4) and crotisol (F) secretion of the cells in several minutes. The induction of P450scc protein amount and StAR mRNA amount were detected with Western Blotting and RT-PCR, respectively. Specific inhibitors of JAK2, MEK/ERK1/2 and PKA were used to study the signal pathways of PRL. The acute induction on steroid secretion was reduced by all three inhibitors. Interestingly, both inhibitors of JAK2 and PKA reduced PRL-induced P450scc protein amount, but MEK/ERK1/2 inhibitor did not. Obviously, PRL activates P450scc expression via signaling pathway of JAK2 and PKA and an unknown steroidogenic protein via MEK/ERK1/2 to stimulate adrenal steroidogenesis.