請用此 Handle URI 來引用此文件:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/76166
標題: | 鯔魚成熟過程中血清類固醇型態及其結合蛋白特性之研究 Steroidal Profiles and Characteristics of Serum Steroid-Binding Proteins during Oocyte Maturation in Grey Mullet (Mugil cephalus L.) |
作者: | 施怡如 |
出版年 : | 1995 |
學位: | 碩士 |
摘要: | 鯔魚(Mugil cephalus L.)俗稱烏魚,具有雜食性,魚體成長快速,環境之耐性及抗病力強等特點,是相當具有經濟價值之養殖魚種。鯔魚屬於冬季產卵型,雌魚的生殖是透過下視丘-腦下垂體一卵巢系統之控制調節,當環境光照週期減短、溫度變低,會誘使卵細胞發育成熟,若加以激素處理,將能有效促進卵細胞最後成熟之進行。俟至目前,烏魚在蓄養環境下產卵仍需激素之處理。有鑑於此,研究烏魚最後成熟過程之生理調控機制,將有助於烏魚種魚之繁養殖。 本研究選用生長達性腺成熟,平均卵徑0.6 mm以上之烏魚,以肌肉注射方式,將相當於腦下垂體促性腺激素之胎盤性性腺激素(Puberogen)注入魚體中,誘導卵細胞進入最後成熟階段。在探討烏魚最後成熟過程,血清類固醇含量變化與性成熟度之相關性時,經放射性免疫分析法(RIA)測定血清類固醇含量之結果,雌二醇含量在最後成熟過程中急遽下降,因而推測,雌二醇與卵細胞成熟作用為間接的,且減少雌二醇對腦下垂體促性腺激素之迴饋作用,有助於腦下垂體促性腺激素的分泌。而血清中睪固酮含量和性成熟度之相關性,與雌二醇呈相似之變動趨勢,顯示睪固酮確為雌二醇生成之前驅物,而且卵巢類固醇生成途徑在最後成熟階段發生轉移,以分泌21碳類固醇為主。 關於黃體激素,17α單羥基黃體激素及17α,20β雙羥基黃體激素等21碳類固醇,血清中含量在卵細胞進入最後成熟階段,均呈現上升之趨勢,在排卵期前的發育過程,三種類固醇量明顯高於卵黃生成時期,於排卵期後才平緩下降至與卵黃生成時期相近之含量。其中又以17α.20雙羥基黃體激素,含量上升現象最為顯著,分別在卵核居中期和卵核崩裂期出現二高峰,由此可誰知,17α.20β雙羥基黃體激素應共有誘導卵細胞成熟之功能。 至於血清中類固醇的運送,是由一群特殊之類固醇結合蛋白所攜帶。類固醇結合蛋白對其所攜帶之類固醇分子,具有結合專一性,兩者之結合親和力(Binding affinity)極高,同時兩者之間亦具有迅速解離(Rapid dissociation)之特性,使標的組織快速有效地與類固醇相辨識結合。本研究亦針對類固醇結合蛋白之結合特性,探討與類固醇含量及性成熟度兩者之相關性。在分析類固醇結合蛋白性質時,選用平衡透析法,此一測定方法測得之專一性結合量遠比活性碳吸附法測值精確。以不同濃度放射性標幟類固醇進行結合分析,得到一結合之飽和曲線,顯示在烏魚血清中確實存在與類固醇進行專一性結合之蛋白質。經由Scatchard plot結合平衡分析,雌二醇和睪固酮之結合蛋白具有單一形式結合位置,對此二激素表現出一定值之親合能力(Ka),而21碳類固醇,包括黃體激素、17α單羥基黃體激素17α,20β雙羥基黃體激素,其結合蛋白出現兩個不同形式結合位置,在低濃度時,結合性質呈現高親和力,隨濃度增加,表現出較低親和力,同時攜帶容量增高。 此外,關於血清中類固醇濃度與結合蛋白之專一結合能力,在烏魚研究結果顯示,兩者無相關性存在。而根據類固醇結合蛋白之結合特異性區分,發現烏魚血清中,18碳及19碳類固醇,由同一結合蛋白運送,此類固醇結合蛋白對19碳類固醇的親和力明顯高於18碳類固醇。而21碳類固醇似由另一結合蛋白攜帶,且此結合蛋白對黃體激素之結合專一性高於17α單羥基黃體激素及17α,20β雙羥基黃體激素,顯示21碳類固醇分子其C-20或C-17位置有羥化現象(Hydroxylation),會降低21碳類固醇結合蛋白與之形成鍵結的能力。 The grey mullet. Mugil cephalus L. is one of commercially important teleosts suitable for culture. The ovarian maturation of female could be induced out-of-season by the enviromental manipulations of photoperoid and temperature. Onset of vitellogenesis is timed by the enviromental conditions; the short photoperoid (6L/18D) plays a dominant role in triggering oocyte vitellogenesis, while temperature regulated vitellogenesis towards functional maturity, at which the ovulation is readily induced by hormonal intervention. The steroid profiles of five steroids in serum. estradiol-17β(E2). testosterone (T) progesterone (P). 17α-hydroxyprogesterone (17α-P) and 17α, 20β-dihydroxy-4-pregene-3-one (17α, 20β-DHP) and the characteristics of serum steroid- binding proteins in grey mullet during oocyte maturation induced by human chorionic gonadotropins (hCG) were monitored. Serum levels of E2 and T decreased as final oocyte maturation progressed. While the levels of P. 17α-P and 17α. 20β-DHP all increased significantly coincident with the initiation of oocyte maturation. The result indicates the steroigenic pathway of ovary was shift from C18 to C21 steroids. Among other tested C21 steroids. 17α. 20β-DHP level was strikingly elevated during the maturation process peaked at subperipheral and GVBD stages. The finding way suggests that 17α, 20β-DHP is likely the maturational steroid in grey mullet. The detection of specific steroids binding serum proteins was determined by equilibrium dialysis method. Binding properties for E, and T were analyzed according to Scatchard and by a linear plot, and indicated a single class of binding sites, association constants (Ka) ranged from 7 to 2x10-4 pMol-1 of E2 and from 2 to 4xl0-4 pMol-1 of T; and binding capacities (N) from 0.52 to 3.69 pmole/mg protein of E2 and from 7.41 to 30.94 pmole/mg protein of T during oocyte maturation. For P. 17α-P and 17α, 20β-DHP, Scatchard plot revealed two different binding sites: a hight affinity binding site with Ka of 10-2~10-3 pMol-1 and N of 0.01~0.42 pmole/mg prootein: and a low affinity biinding site with Ka of 10-3~l0-5 pMol-1 and N of 0.04~4.06 pmole/mg prootein. The results demonstrated no correlation between serum steroids and steroid-binding capacity during the maturational process in grey mullet. By competitive binding experiments serum proteins may be classified in two groups according to their specificity: a single protein binding specifically to C18 (E2) and C19 (T) steroids. and the other binding specifically to C21 (P. 17α-P and 17α. 20β-DHP) steroids. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/76166 |
全文授權: | 未授權 |
顯示於系所單位: | 漁業科學研究所 |
文件中的檔案:
沒有與此文件相關的檔案。
系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。