Use of a Radioimmunoassay Which Detects C21Steroids with a 17,20β-Dihydroxyl Configuration to Identify and Measure Steroids Involved in Final Oocyte Maturation in Female Plaice (Pleuronectes platessa)

Biology of Reproduction

Vermeirssen

et al. 1997

Spermiating striped bass, a perciform fish, were treated with two controlled-release gonadotropin-releasing hormone agonist (GnRHa)-delivery systems, and the resulting changes in plasma gonadotropin II (GTH II), testosterone (T), 11-ketotestosterone (11-KT), 17,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P), and 17,20beta,21-trihydroxy-4-pregnen-3-one (17,20beta,21-P) were correlated with changes in milt production and sperm density. GnRHa-delivery systems induced a sustained elevation of plasma GnRHa and GTH II for 14 days. Plasma T levels were unchanged after GnRHa treatment, while 11-KT levels increased significantly. Plasma 17,20beta-P also increased after GnRHa treatment and remained elevated compared to levels in controls, while plasma 17,20beta,21-P levels were unaffected. Both GnRHa-delivery systems induced many-fold increases in total expressible milt, lasting throughout the 14 days of the study. Sperm density decreased 2 days after GnRHa treatment, with a subsequent increase by Day 7. This study demonstrates that GnRHa-delivery systems induce a sustained elevation of plasma GTH II levels in striped bass, resulting in a long-term enhancement of milt production. The endocrine changes observed suggest that 11-KT and 17,20beta-P, but not 17,20beta,21 -P, are mediating the effects of GTH II on spermiation.

Section: Hormonal Measurementsmentioning

confidence: 99%

Changes in Plasma Gonadotropin II and Sex Steroid Hormones, and Sperm Production of Striped Bass after Treatment with Controlled-Release Gonadotropin-Releasing Hormone Agonist-Delivery Systems1

Mylonas

Biology of Reproduction

Vermeirssen

et al. 1997

“…Concentrations of 3 ,17,20 -P-5 were measured with a radioimmunoassay which specifically detects steroids with a 17,20 -dihydroxyl configuration (17,20 -RIA; Scott et al, 1997). It has been shown that c. 80% of the cross-reactivity in female plaice plasma is accounted for by 3 ,17,20 -P-5 and c. 20% by 3 ,17,20 -P-5 .…”

Section: Radioimmunoassay Of Steroids and Gnrhamentioning

confidence: 99%

“…and 5 -pregnane-3 ,17,20 -triol 20-sulphate (3 ,17,20 -P-45 20-S) have been identified recently as major circulating steroids in the bloodstream of reproductively mature female plaice Pleuronectes platessa L. Scott et al, 1997). It is likely, though not yet proven, that these steroids are derived from 17,20 -dihydroxy-4pregnen-3-one (17,20 -P), the putative maturation-inducing steroid (MIS) in plaice.…”

Section: Introductionmentioning

confidence: 99%

Prolonged‐release gonadotrophin‐releasing hormone analogue implants enhance oocyte final maturation and ovulation, and increase plasma concentrations of sulphated C₂₁ steroids in North Sea plaice

Journal of Fish Biology

Witthames

Carolsfeld

1999

Reproductively mature female plaice were implanted with or without 50 g of gonadotrophinreleasing hormone analogue (GnRHa), suspended in either coconut oil or methacrylate resin. The weight of the GnRHa-treated fish increased significantly (due to hydration of the oocytes) and reached a peak between 10 and 14 days. The fish produced several batches of eggs, which were consistently bigger than those produced by control fish. Plasma concentrations of free 17 -oestradiol and glucuronidated testosterone rose briefly (4 days) in response to the GnRHa, but then fell continuously till the end of the experiment (20 days). Plasma concentrations of sulphated 5 -pregnane-3 ,17,20 -triol and 5 -pregnane-3 ,17,20 -triol (which are putative metabolites of 17,20 -dihydroxy-4-pregnen-3-one, the oocyte maturation-inducing steroid) increased significantly at 4 days and reached a peak between 12 and 16 days. Concentrations were still very elevated on day 20. Plasma concentrations of sulphated 3 ,17,21-trihydroxy-5pregnan-20-one showed a slight increase on day 4 but did not change thereafter. There was a highly significant difference in the amounts of GnRHa released into the bloodstream by the two methods of administration on day 4. However, this was not matched by significant differences in the concentrations of any of the steroids. 1999 The Fisheries Society of the British Isles

“…This was evaporated and the residue redissolved in 1 ml assay buffer. It was shown by Scott et al (1997), that free C 21 steroids in female plaice plasma occur at concentrations 10-100 times lower than in their sulphated forms. Therefore, for assay of the sulphated C 21 steroids, the presence of these free steroids was ignored and 25 l of untreated plasma were mixed directly with 4 ml trifluoroacetic acid(TFA)/ethyl acetate (1·4/100 v/v) in a glass tube.…”

Section: Radioimmunoassay Of Steroidsmentioning

confidence: 99%

Plasma concentrations of ovarian steroids in relation to oocyte final maturation and ovulation in female plaice sampled at sea

Journal of Fish Biology

Witthames

Turner

et al. 1998

Blood plasma concentrations of free 17 -oestradiol, free testosterone and glucuronidated testosterone were strongly positively related to the percentage of vitellogenic oocytes remaining in the ovaries of plaice Pleuronectes platessa caught at sea-being at their highest in pre-spawning (stage IV) females (i.e. those in which the oocytes were close to fully grown, but had not yet entered the stage of final maturation). In contrast, the concentrations of free and sulphated 17,20 -P, 3 ,17,20 -P-5 , and 3 ,17,21-P-5 were at their lowest in stage IV females. Free 17,20 -P (the putative maturation-inducing steroid) became only slightly elevated (less than twofold) during spawning (i.e. in stage V and VI females with hydrated and/or ovulated eggs). Sulphated 17,20 -P and 3 ,17,21-P-5 became slightly more elevated (three-to fourfold). However, sulphated 3 ,17,20 -P-5 concentrations increased 30-fold and were at their highest in fish in which only 40% of vitellogenic oocytes remained in the ovaries. Sulphated 17,20 -P, 3 ,17,20 -P-5 and 3 ,17,21-P-5 concentrations were significantly positively related to hyaline oocyte batch size; and sulphated 17,20 -P and sulphated 3 ,17,20 -P-5 were significantly negatively related to the degree of hydration of the hyaline oocytes. None of the steroid concentrations, however, was related to the time of capture. More ovulated females were found in the afternoon than at any other time of the day. 1998 The Fisheries Society of the British Isles