Vermeirssen E L, Scott A P, Mylonas C C, Zohar Y
Lowestoft Laboratory, The Centre for Environment, Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, Suffolk, NR33 0HT, United Kingdom.
Gen Comp Endocrinol. 1998 Nov;112(2):163-77. doi: 10.1006/gcen.1998.7132.
Spermiating male plaice were caught in the North Sea and acclimatised to laboratory conditions. In two experiments, males were injected intramuscularly with either microspheres or pellets containing gonadotrophin-releasing hormone agonist (GnRHa). Blood was sampled at 2- to 5-day intervals. Individual blood plasma specimens were assayed for testosterone, 5beta-reduced, 3alpha-hydroxy ("5beta,3alpha") steroids and sulphated 17, 20beta-dihydroxy ("17,20beta") steroids. Pooled plasma samples were also assayed for free and sulphated 17, 20beta-dihydroxy-4-pregnen-3-one, free 11-ketotestosterone, and glucuronidated testosterone and 11-ketotestosterone. Plasma concentrations of all steroids were significantly elevated by GnRHa from 2 to 5 days onwards following treatment. The most marked changes occurred in the concentrations of the sulphated 17,20beta steroids, which comprised approximately equal amounts of 5beta-pregnane-3alpha,17,20beta-triol 20-sulphate (3alpha,17, 20beta-P-5beta-S) and 5beta-pregnane-3beta,17,20beta-triol 20-sulphate, rising from ca. 1 to 30-80 ng/ml in the first and from ca. 8 to 80 ng/ml in the second experiment. Concentrations of 5beta, 3alpha steroids matched those of 17,20beta steroids in one experiment. However, in the other experiment, the two RIAs yielded highly disparate results in about 50% of the fish (including males in the control group). The plasma of these fish contained excessive amounts of 5beta,3alpha-immunoreactive material between 10 and 25 days. This material was identified as 3alpha,17, 21-trihydroxy-5beta-pregnan-20-one 21-sulphate (a metabolite of 11-deoxycortisol). All previous studies have indicated that when plasma concentrations of this steroid are high, so are those of 3alpha,17,20beta-P-5beta-S. This is the first indication that these steroids are regulated independently. In a third experiment, milt fluidity and production were assessed at 10, 15, and 25 days following GnRHa implantation. Milt volume and fluidity were significantly enhanced by the GnRHa treatment.
正在排精的雄性鲽鱼在北海捕获，并使其适应实验室条件。在两项实验中，给雄性鲽鱼肌肉注射含有促性腺激素释放激素激动剂（GnRHa）的微球或丸剂。每隔2至5天采集一次血液样本。对个体血浆样本检测睾酮、5β-还原、3α-羟基（“5β,3α”）类固醇以及硫酸化的17,20β-二羟基（“17,20β”）类固醇。对合并的血浆样本也检测游离和硫酸化的17,20β-二羟基-4-孕烯-3-酮、游离11-酮睾酮以及葡萄糖醛酸化的睾酮和11-酮睾酮。GnRHa处理后从第2天到第5天起，所有类固醇的血浆浓度均显著升高。最显著的变化发生在硫酸化的17,20β类固醇的浓度上，其包含大约等量的5β-孕烷-3α,17,20β-三醇20-硫酸盐（3α,17,20β-P-5β-S）和5β-孕烷-3β,17,20β-三醇20-硫酸盐，在第一个实验中从约1 ng/ml升至30 - 80 ng/ml，在第二个实验中从约8 ng/ml升至80 ng/ml。在一项实验中，5β,3α类固醇的浓度与17,20β类固醇的浓度相符。然而，在另一项实验中，两种放射免疫测定法在约50%的鱼（包括对照组中的雄性）中产生了高度不同的结果。这些鱼的血浆在10至25天之间含有过量的5β,3α免疫反应性物质。这种物质被鉴定为3α,17,21-三羟基-5β-孕烷-20-酮21-硫酸盐（11-脱氧皮质醇的一种代谢产物）。所有先前的研究表明，当这种类固醇的血浆浓度高时，3α,17,20β-P-5β-S的血浆浓度也高。这是这些类固醇独立调节的首个迹象。在第三个实验中，在GnRHa植入后的第10、15和25天评估精液流动性和产量。GnRHa处理显著提高了精液体积和流动性。
