• 作者： 季培元; 周俐慧; 謝美華; 林仁壽; 萬家茂
• 作者服務機構： 國立台灣大學畜牧系; 中央研究院動物研究所
• 中文摘要： 腦下腺分祕促腎上皮素（ACTH）過多與不足，均導致生殖內分泌系統功能之紊亂，此現象可間接經由腎上腺皮質分泌類固醇的改變及／或由腦下腺本身ACTH的直接作用來達成。前者已獲明證，而後者乃近十年來爭論之焦點。本研究採用去腎上腺手術（Adx）及 Dexamethasone（Dex）處理，分別促使腦下腺 ACTH釋出增加或減少，進而利用性釋素（GnRH）刺激此等腦下腺，以觀察其分泌 LH的情形。 本實驗選用 Wistar 系雄鼠（200-250g）飼於有溫度調節（20±2°C）及每日光照時間14小時（06：00～20：00）之動物室內，飼料（purina rat chow）及飲水自由採食。取自經 20μg Dex 腹腔注射後一小時者及經去腎上腺手術3及7日者的腦下腺，分別進行腦下腺前葉浸浴培育法，於適當時間用 GnRH 刺激之，收集培養液，以放射免疫分析法及分離腎上腺細胞法分別測定樣本中促黃體素（LH）及促腎上皮素（ACTH）之含量。其結果與對照組比較，顯示經去腎上腺7日組 ACTH 釋出增加，而以 Dex 處理組則降低。二者經 GnRH（5ng）刺激後ACTH 含量及釋出均不受影響，而 LH 釋出顯著低於對照組，故本實驗證實： (1)雄鼠腦下腺 ACTH 活性能直接影響 LH 之釋出，亦即當 ACTH 活性過高或不足時，會令腦下腺對於 GnRH 刺激反應減低。 (2) ACTH 對於生殖系統之直接抑制作用主要存在於腦下腺。 (3) GnRH 未具有使 ACTH 釋出功能。
• 英文摘要： The reproductive function of ani-mals is easily disturbed by the changesof corticotropin (ACTH) status in theabnormal condition. Such influence maybe explanined by the direct and indirectactions of ACTH on the hypothalamo-pituitary-gonadal axis. This study em-phasized on the inhibition of ACTH onthe luteinizing hormone (LH) releasefrom male rat pituitary in vitro inresponse to gonadotropin-releasing hor-mone (GnRH). Dexamethasone (100μg/kg. BW, IP) treatment and adrenalec-tomy (3 and 7 days after operation)were employed as the tool for alteringthe pituitary ACTH contents. Theresponsiveness of pituitary to GnRHwas tested in vitro and the ACTH andLH concentrations in the pituitary andthe incubation medium were measuredwith dispersed adrenal cell techniqueand radioimmunoassay, respectively.The results showed that LH releasefrom pituitary in vitro in response toGnRH (5ng) was significantly reducedin both treated animals when comparedwith that of intact rats, whereas theACTH release was not altered. Thesesuggested that the ACTH may play animportant role on the modulation of LHrelease from the pituitary in situ, ifACTH, under or over the physiologicalcondition, The possible affected sitesof ACTH were also discussed in thetext. It is concluded that the pituitary,itself, is the most likely site for theACTH direct effect on the inhibitionof reproduction.
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