海鰻性腺刺激素對鯉血漿睾固酮含量的影響

Abstract

海鰻性腺刺激素可促進雄鯉血睾漿固酮(testosterone)含量的上升，刺激素處理後15分鐘，血漿睾固酮含量即有顯著增加，2小時反應最大，8小時內維持平台值(plateau)，之後又逐漸下降，此種促進作用具有劑量－效應(dose-response)關係。若於第12小時再注射第二次，可提升至更高的平臺值。 不同種類的性腺刺激素，對促進鯉魚血漿睾固酮含量增加的效應比較，海鰻性腺刺激素較鯉魚性腺刺激素的作用為強，羊黃體刺激素則無作用。 蛋白質合成抑制劑Cycloheximide會抑制鯉魚血漿睾固酮的基礎含量(basal level)，及抑制海鰻性腺素之作用。Theophylline並不能增加鯉魚血漿睾固酮含量或增強海鰻性腺素及羊黃體刺激素的作用。 鯉血漿睾固酮含量具有日週期變化，高?值出現於下午二時，若于此時施予海鰻性腺素，則促進鯉產生睾固酮之反應程度，較所試的其他時間點為大。 鯉魚血漿睾固酮含量與魚體GSI具有密切的關係，且有年週期性之變化，十月以後兩者都逐漸增大，在一至二月達到高?，之後又逐漸下降，顯示鯉魚的生殖季節大約在一至二月。除此之外，鯉魚對外加性腺刺激素的反應程度與魚體血漿睾固酮濃度也呈正相關，即血漿睾固酮濃度愈高，魚體之反應程度也愈大，以一至二月的魚體反應程度最大。

1. The carp plasma testosterone content can be stimulated by pike eel gonadotropin (pPGTH). This effect has dose-response relationship. Significant increase of plasma testosterone content occurred at 15min after administration of pPGTH. The effect of pPGTH on carp plasma testosterone content is gradually increased as the time of pPGTH administration elapses and reached a plateau at 2hr. This plateau is then gradually leveled off after 8hr. The second administration of pPGTH at 12hr after the first pPGTH injection can cause the appearance of second plateau of plasma testosterone content. 2. In addition to pGTH, carp GTH can but ovine luteinizing hormone(oLH) can not stimulate the increase of carp plasma testosterone content. 3. Cycloheximide can inhibit the effect of pGTH on the increase of carp plasma testosterone content. No effect is observed when theophylline is administered alone or co-administered with pGTH or on carp plasma testosterone content. 4. Circadian rhythm of carp plasma testosterone content is found. The peak is at 14:00. At this time the exogenous pGTH elicit higher response than at other time intervals. 5. Annual rhythm of carp plasma testosterone content is also found. The plasma testosterone content is correlated well with the breeding cycle of carp, i.e., there is positive correlation between gonadosomatic index (GSI) and plasma testosterone content. Higher GSI and plasma testosterone content of carp are found in January and Febuary. The response of carp toward exogenous pGTH is also higher when carp has higher plasma testosterone content.