鯉魚性腺刺激素對睪丸雄性素生合成效應之研究

Abstract

本實驗係使用高壓液相色層分析儀解析固酮類物質，藉以調查鯉魚性腺刺激素對鯉魚睪丸雄性素生成之效應，並闡釋鯉魚睪丸內雄性素生合成之途徑。 不論在離體或活體情況下，鯉魚性腺刺激素的處理皆能促進鯉魚睪丸內固酮類的?生；尤以11-Ketotestosterone，11β-Hydroxy-androstenedione和Progesterone的提高為然。但是鯉魚性腺刺激素的這種效應可被蛋白質合成抑製劑，Cycloheximide，所阻斷。同樣的，11-Ketotestosterone和11β-Hydroxyandrostenedione的生成也會被11β-羥化?的抑製劑，Metyrapone所抑制。然而，在Metyrapone的作用下，Progesterone則會堆積。 離體情況下，鯉魚睪丸組織也能將外加21碳或19碳的類固醇轉變為其他形式的固酮醇。19碳的外加受質很容易就被轉為11-Ketotestosterone，然而21碳則否。而且，性腺刺激素以及蛋白質抑制劑CycloHeximide並不影響外加受質在睪丸組織培育下轉變的效應。 從這些實驗數據所推衍，鯉魚的睪丸內應存有3β-Hydroxysteroid dehydrogenase/△4.△5-Isomerase， 11β-Hydroxylase,17α-Hydroxylase, C17-20 Desmolase, 21-Hydroxylase,等?。這系列的?是常設於睪丸組織內而且相當穩定。 鯉魚睪丸組織內也具有cortisol，其在離體組織培育下會抑制11β-Hydroxyandrostenedion轉變成11-Ketotestosterone，可能具有調節雄性素合成之生理功能。 歸納實驗的結果，我們認為鯉魚性腺刺激素對雄性素生成的作用效應是在膽固醇(cholesterol)變成Pregnenolone的步驟上。而推演其雄性素生合成的途徑曾是： Pregnenolone→Progesterone→11-Hydroxyproge-sterone→21-Deoxycortisol→11β-Hydroxyandr-stenedione→Adrenosterone→11-Ketotestosteron。

The aim of this study is toward the investigation of the effect of carp gonadotropin (cGTH) on steroid production by carp testis and the elucidation of androgen biosynthetic pathway in carp testis. In this study, analysis of steroids are performed by high pressure liquid chromatography. cGTH can stimulate steroid production by carp testis either by in vivo or j vivo treatment. The most significant effect of cGTH is the enhancement of the production of 11-ketotestosterone, 11β-hydroxyandrostenedione and progesterone. This stimulatory effect of cGTH is completely abolished by cycloheximide, a protein synthesis inhibitor. Similarly, stimulatory effect of cGTH on the production of 11-ketotestos-terone and 11β-hydroxyandrostenedione is also inhibited by metyrapone, an inhibitor of 11β-hydroxylase. However, under the action of metyrapone, progesterone are accumulated. Carp testis is able to convert exogenous C21 and C19 steroids into other forms of steroids in vitro. Exogenous C19 steroids can be converted into 11-ketotestosterone but C21 steroids cannot to be so. Addition of cGTH and cycloheximide do not affect the conversion of C21 and C19 steroid by carp testis in vitro. From these experimental data, it is inferred that carp testis possesses following enzymatic activities: 3β-hydroxysteroid dehydrogenase/△4, △5-isomerase, 11β-hydroxylase, 17α-hydroxy1ase, C17-20 desmolase, 21-hydroxylase. These enzymes are constitutional and fairly stable. Carp testis also possesses cortisol. It may involve in the regulation of androgen synthesis in carp testis since it can inhibit the conversion of 11β-hydroxyandrostenedione to 11-ketotestosterone in vitro. From the present experimental results, it is concluded that the major effect of cGTH on androgen production is at the step of conversion of cholesterol to pregnenolone and that the biosynthetic pathway of androgen is as pregnenolone→progesterone→11β-hydroxyprogesterone→21-deoxycortisol→11β-hydroxyandrostenedione→adrenosterone→11-ketotestosterone.