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1.
The annual reproductive cycle of walleye (Stizostedion vitreum) was characterized by documenting changes in gonadal development and serum levels of estradiol-17β (E2), testosterone (T), 17α,20β-dihydroxy-4-pregnen-3-one (17,20-P), and 11-ketotestosterone (11-KT) in wild fish captured from upper midwestern lakes and rivers throughout the year. Fish from the populations used in this study spawn annually in early- to mid-April. Walleye showed group synchronous ovarian development with exogenous vitellogenesis beginning in autumn. Oocyte diameters increased rapidly from ∼ 200 μm in October to ∼ 1,000 μm in November, and reached a maximum of 1,500 μm just prior to spawning. Changes in gonadosomatic indices (GSIs) paralleled changes in oocyte diameters. Serum E2 levels in females increased rapidly from low values in October (< 0.1 ng ml−1) to peak levels of 3.7 ng ml−1 in November, coinciding with the period of the most rapid ovarian growth. Subsequently, E2 levels decreased from December through spawning. Serum T levels exhibited a bimodal pattern, increasing to 1.6 ng ml−1 in November, and peaking again at 3.3 ng ml−1 just prior to spawning. We detected 11-KT in the serum of some females at concentrations up to 5.6 ng ml−1, but no seasonal pattern was apparent. In this study (unlike our results in a related study) 17,20-P was not detected. In males, differentiation of spermatogonia began in late August, and by January the testes were filled (> 95% of germ cells) with spermatozoa. Mature spermatozoa could be expressed from males from January through April. GSIs ranged from 0.2% (post-spawn) to 3.2% (pre-spawn). Serum T levels rose from undetectable levels in post-spawn males to 1.6 ng ml−1 by November, remained elevated throughout the winter, and peaked at 2.8 ng ml−1 I prior to spawning. Levels of 11-KT in males remained low (< 10 ng ml−1, from post-spawning through January, then increased significantly by March and peaked just prior to spawning at 39.7 ng ml−1. Our results indicate that vitellogenesis and spermatogenesis are complete or nearly so, in walleye by early winter, and suggest that it may be possible to induce spawning in this species several months prior to the normal spawning season by subjecting fish to relatively simple environmental and hormonal treatments.  相似文献   

2.
The present study is concerned with pheromone communication in tench (Tinca tinca L.), establishing firstly whether males have a high olfactory sensitivity to some typical teleost sex steroids and prostaglandins; and secondly whether males and females might be able to synthesise and release some of these steroids into the water. The C21 steroid, 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) was found to give large electro-olfactogram responses with an estimated threshold of detection of 10−12 M. The male tench were equally sensitive to glucuronidated 17,20β-P (10−11.6 M) but 100 times less sensitive to sulphated 17,20β-P (11−9.7 M). Preliminary data from cross-adaptation studies suggest that both the free and conjugated forms are detected by the same olfactory receptor(s). Male tench also had high olfactory sensitivity to prostaglandin F2α (PGF2α) and 15-keto PGF2α (11−11.5 and 10−11.4 M). They were relatively insensitive, however, to testosterone (T), androstenedione (AD), 11-ketotestosterone (11-KT), 17β-oestradiol (E2), 17,20β,21-trihydroxy-4-pregnen-3-one (17,20β,21-P) and 17,20α-dihydroxy-4-pregnen-3-one (17,20α-P). Radioimmunoassays were used to measure the steroids in plasma and water and all samples were processed for the measurement of free, sulphated and glucuronidated fractions. In females, free 17,20β-P, 17,20α-P, free and glucuronidated T, and AD in plasma showed the largest increases in response to injection with mammalian gonadotropin-releasing hormone analogue (GnRHa) or Ovaprim (a mixture of GnRHa and a dopamine inhibitor). Free 17,20β-P was released into the water at the greatest rate. Plasma concentrations of the two conjugated forms of 17,20β-P were also elevated 18 h after the administration of GnRHa, but not by as much as the free steroid. In males, AD and 11-KT showed the greatest increase in response to GnRHa and were moreover released into the water at a higher rate in the treated group than in the control. The data support a possible pheromonal role for free and glucuronidated 17,20β-P. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

3.
Testes from spermiating goldfish were incubated with [3H]17-hydroxyprogesterone. The major products in the unconjugated fraction were identified as androstenedione, androstenetrione, 11-β-hydroxyandrostenedione, 11-ketotestosterone, 17,20α-dihydroxy-4-pregnen-3-one (17,20αP) and 11-deoxycortisol. Testosterone was present predominantly in the glucuronide fraction, but yields were low (1–3%). The major components of the sulfate fraction were 17,20αP and 11-deoxycortisol. The identification of cortisone in low yield (< 2.5010) in both the free and sulfate fractions is the first report of corticosteroid biosynthesis by a teleost testis. The high yields of 17,20αP and 11-deoxycortisol and their sulphates suggests that their possible role in spermiation of the goldfish should be further investigated.  相似文献   

4.
Testosterone, 3,17-dihydroxy-5-pregnen-20-one, 17,20-dihydroxy-4-pregnen-3-one (17,20P) and 5-pregnane-3,17,20-triol were identified as the major metabolites of [3H] 17-hydroxyprogesterone in ovarian incubations of the European catfish Silurus glanis. 17,20P and the reduced triol were present only in ovaries from fish primed with carp hypophysial homogenate (chh) while testosterone yields were significantly higher in controls than in treated fish. 11-Ketotestosterone, 11-hydroxytestosterone and 17,20-dihydroxy-4-pregnen-3-one (17,20P) were identified as the major metabolites of [3H]17-hydroxyprogesterone in in vitro incubations of testes of a spermiating catfish. There was no significant production of conjugates or other water soluble metabolites by either sex. The stimulation of plasma 17,20P, 17,20P and 11-hydroxytestosterone by chh in primed but not control males suggests that the role of these steroids in spermiation should be further examined.  相似文献   

5.
A distinct shift in steroidogenesis from testosterone to 17α-hydroxyprogesterone occurs in the salmonid ovarian thecal cell layers immediately prior to oocyte maturation, and is a prerequisite for the production of 17α,20β-dihydroxy-4-pregnen-3-one (maturation-inducing hormone of salmonid fishes) by granulosa cells during oocyte maturation. 17α-Hydroxylase/17,20-lyase cytochrome P-450 (P-45017α) and 3β-hydroxysteroid dehydrogenase/Δ5?4-isomerase (3β-HSD) are the two major steroidogenic enzymes involved in the production of 17α-hydroxyprogesterone and testosterone. Using mammalian cDNA probes, we isolated and characterized full-length cDNAs encoding these two enzymes from a rainbow trout (Oncorhynchus mykiss) ovarian thecal cell cDNA library. The cloning of 2.4-kilobase cDNA encoding P-45017α and transient expression of this clone in nonsteroidogenic monkey kidney tumor COS-1 cells have recently been reported (Sakai et al. 1992). We have isolated a 1.4-kilobase cDNA which is hybridized to the mammalian 3β-HSD cDNAs. Expression of this cDNA in COS-1 cells led to the production of an enzyme which is capable of converting dehydroepiandrosterone to androstenedione. In this study, enzymatic activities and expression of rainbow trout ovarian P-45017α and 3β-HSD are discussed in relation of the steroidogenic shift occurring in the ovarian follicle layers.  相似文献   

6.
The relationship between plasma and ovarian levels of gonadal steroids was examined in two New Zealand fish species with multiple spawning cycles of differing length. Snapper (Pagrus auratus) have a daily cycle of oocyte development, ovulation and spawning, whereas demoiselles (Chromis dispilus) spawn over 2–3 days during a repeat spawning cycle of 7–9 days. Ovarian and plasma levels of the gonadal steroids 17β-estradiol (E2), testosterone (T), 17-hydroxyprogesterone (17P) and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP) were measured in reproductively active fish captured from the wild. Ovarian levels of E2, T and 17P changed in relation to spawning cycle and gonad stage in both snapper and demoiselles. E2 and T levels were detectable at all times, but highest during vitellogenesis in both species. Cyclic changes of 17P occurred in both species, and levels appeared to depend on the rate of conversion of 17P to other hormones. No changes in ovarian levels of 17,20βP were detected in relation to stage of the spawning cycle in snapper; however, ovarian levels of 17,20βP were highest in demoiselles before spawning when fish undergoing final oocyte maturation predominated. Plasma levels of E2 and T were strongly correlated with ovarian concentrations (r=0.850 and r=0.819 for E2 and T respectively) in demoiselles but there was poor correlation between ovarian and plasma levels of 17P and 17,20βP (r=0.004 and 0.273 respectively), or between ovarian and plasma levels of E2, T, 17P or 17,20βP of snapper (r=0.135, 0.277, 0.131 and 0.279). The poor correlation between plasma and ovarian levels of some steroid hormones suggests that plasma concentrations of steroids may not adequately reflect the reproductive status of the fish during short-term cyclic ovarian changes. It is suggested that this disparity is likely to be most marked in species with ovulatory periodicity of short duration.  相似文献   

7.
Significant plasma 17,20β-dihydroxy-4-pregnen-3-one peaks were measured for the first time in female Eurasian perch, Perca fluviatilis, during the pre-ovulatory period, reaching 3.5 ng ml?1, but was not synchronized with final maturation and ovulation stages.  相似文献   

8.
The in vitro effects of several steroids on the maturation of intact white sturgeon (Acipenser transmontanus) ovarian follicles were investigated. At the highest concentration (1024 ng ml–1 for the C21 steroids and 1139 ng ml–1 for the C19 steroids), all of the C21 steroids tested, progesterone (P4), 17-hydroxyprogesterone (17OHP), 17,20-dihydroxy-4-pregnen-3-one (17,20-P), 17,(20,21-trihydroxy-4-pregnen-3-one 20-S), 11-deoxycortisol (S) and cortisol (F), as well as testosterone (T) induced germinal vesicle breakdown (GVBD) at 14 and 22 h. At 6 h, only P4 and 17,20-P induced maturation at the highest concentration (1024 ng ml–1). At 14 and 22 h, 11-deoxycortisol was the most potent steroid inducer of GVBD followed by P4, 17OHP, 17,20-P, and 20-S. The steroid 11-hydroxytestosterone (11OHT) was completely ineffective at all concentrations and exposure times. The C21 steroids induced oocyte maturation at concentrations ranging from 4 to 1024 ng ml–1, whereas T induced GVBD at 225 to 1139 ng ml–1. Calculation of the mean effective concentration that induced 50% GVBD (EC50) from the 22 h incubations revealed the following order of potencies: S > P4 > 17OHP > 17,20-P > 20-S >> F > T. These bioassay results, together with previous findings on the endogenous production of steroids by ovarian follicles from gonadotropin-primed females, indicate that more than one steroid has a biological role in the resumption of meiosis in sturgeon oocytes and provides empirical evidence for P4, 17OHP, S, 20-S, and 17,20-P as maturation-inducing steroids in white sturgeon.  相似文献   

9.
Roach ovaries converted 17-hydroxyprogesterone to 17,20-dihydroxy-4-pregnen-3-one (17,20P) and to glucuronides of testosterone and 17,20P. Small amounts of 5-pregnane-3- and -3, 17, 20-triols, 7-hydroxy-5-reduced metabolites and 17,20-dihydroxy-4-pregnen-3-one (17,20P) were also formed. Rudd ovaries converted this substrate mainly to 17,20P, 5-pregnane-3- and -3,17,20-triols, 17,20-dihydroxy-5-pregnan-3-one and testosterone glucuronide. The main metabolites of progesterone with both species were 17,20P, 5-pregnane-3,17,20-triol and 7-hydroxy-5-reduced steroids. Rudd ovaries formed, in addition, 17,20-dihydroxy-5-pregnan-3-one from progesterone. The pattern of metabolites was markedly altered when the concentration of substrate was increased from 42ng to 1 µg or 100 µg. At the highest concentration, glucuronides and polar steroids were not detectable, while at low concentrations they accounted for over 50% of the metabolites. 20-Hydroxysteroid dehydrogenase was shown to have a very high capacity, producing 21–47 µg 17,20P from 100 µg 17-hydroxyprogesterone substrate with 200 mg ovarian tissue in 5h.  相似文献   

10.
Hormonal and pheromonal control of spawning behavior in the goldfish   总被引：6，自引：0，他引：6  
Species that employ sexual reproduction must synchronize gamete maturity with behavior within and between genders. Teleost fishes solve this challenge by using reproductive hormones both as endogenous signals to synchronize sexual behavior with gamete maturation, and as exogenous signals (pheromones) to synchronize spawning interactions between fish. This dual role of hormonal products is best understood in the goldfish, an external fertilizer with a promiscuous mating system. Female gonadal growth and vitellogenesis is stimulated by 17β-estradiol (E2) which also evokes release of a recrudescent pheromone. At the completion of vitellogenesis, ovarian E2 production drops and plasma testosterone increases, sensitizing the female gonadotropin II (luteinizing hormone; LH) system to environmental cues (temperature, spawning substrate, pheromones). These cues eventually trigger a LH surge that alters steroidogenesic pathways to favor the production of progestins including 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P). Plasma 17,20β-P stimulates oocyte maturation but is also released to the water along with sulfated 17,20β-P and androstenedione to serve as a preovulatory pheromone. This pheromone stimulates male behavior, LH release, and sperm production. At the time of ovulation, females become sexually active in response to prostaglandin F2α (PGF2α) synthesized in the oviduct. PGF2α and its metabolites are released as a postovulatory pheromone that induces male spawning behavior which further increases male LH and sperm production. Androgenic hormones are required for male behavior and LH release. Although goldfish are gonochorists, hormone treatments can induce heterotypical functions in adults. Similar findings in other fish demonstrate that a sexually bipotential brain is not restricted to hermaphroditic fishes. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

11.
Incubation of follicular cells from postvitellogenic spotted wolffish ovaries with tritiated steroid precursors revealed that granulosa cells were able to convert 17-hydroxyprogesterone (17-P) to 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) and androstenedione. Theca cells had limited ability to synthesise additional steroids from 17-P but converted 17,20β-P to 17,20β-P sulphate. Neither of the two cell layers was able to synthesise 5β-pregnane-3α,17,20β-triol-20-sulphate (3α,17,20β-P-5β-S) which is found in high concentrations in plasma. 17,20β,21-trihydroxy-4-pregnen-3-one (17,20β,21-P), 17,20β-dihydroxy-5β-pregnan-3-one (17,20β-P-5β) and 17,20β-P were most potent in inducing germinal vesicle breakdown (GVBD). Sulphation of 17,20β-P resulted in loss of GVBD inducing activity.  相似文献   

12.
This study examined the changes in plasma steroids during natural (Experiment 1) and induced (Experiment 2) final maturation in yellow perch Perca flavescens. In experiment 1, ovulating yellow perch were stripped of eggs and blood samples collected to determine the concentrations of testosterone (T), estradiol-17β (E2), and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP). Eggs from individual females were weighed and fertilized. Fertilization rate was determined at the embryo eyed stage. In experiment 2, females were randomly assigned to one of the following treatment groups: (1) saline (0.7% NaCl), (2) des-Gly10[D-Ala6] LHRH-ethylamide (100 μg LHRHa/kg), and (3) LHRHa plus 17,20βP (100 μg LHRHa/kg + 2 mg 17,20βP/kg). Fish were injected intraperitoneally with two doses at a two-day interval. Blood was collected prior to injections and at the time of ovulation/spawning and concentrations of T, E2, and 17,20βP (free and conjugated) were determined. In experiment 1, low concentrations of 17,20βP were recorded at spawning. In experiment 2, all surviving fish injected with LHRHa (5 of 5) released their eggs spontaneously during the week following injections. None of the surviving control fish (0 of 5) ovulated during this period, whereas only 1 of 3 surviving fish injected with LHRHa + 17,20βP released eggs. In the control group, concentrations of E2 and 17,20βP did not show significant differences over the experimental period, whereas plasma T concentrations increased significantly. In fish injected with LHRHa, the concentrations of T and 17,20βP increased significantly after the first injection but then declined at ovulation/spawning. It also appears that 17,20βP was conjugated to its sulfated form. Mortality reached 62.5% in the group injected with LHRHa + 17,20βP indicating that this treatment was severe. Thus, LHRHa alone appears highly effective in inducing ovulation in yellow perch. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

13.
Goldfish, carp and trout gills were incubated with 3H-17-hydroxyprogesterone (17P). With goldfish gills, the metabolites were 17,20-dihydroxy-4-pregnen-3-one (17,20P; 82%), 17,20-dihydroxy-4-pregnen-3-one (17,20P; 8%), 11-ketotestosterone (KT) glucuronide (5.4%) and 17,20P glucuronide (0.2%). Sulfates were not detected. Carp gills converted 17P into 17,20P (11.2%), 17,20P (9.6%), KT (8.4%), glucuronides of 17,20P (1.3%) and 17,20P (1.6%) and sulfates of 17,20P (5.1%) and 17,20P (7.2%). 17,20P (38% free, 1.8% glucuronide and 21.1% sulfate) was the sole metabolite of 3H-17P in trout gill incubations. In the presence of high (10; µg ml-1) substrate concentration, cyprinid gills gave predominantly free 17,20P, while trout gills yielded only free 17,20P. Production of 17,20P, predominantly as its sulfate, from endogenous precursors was demonstrated in trout gills but was not stimulated by trout primary extract. Our results demonstrate for the first time the steroidogenic potential of teleost gills and suggest that they may play a role in secretion of pheromones in some species.  相似文献   

14.
A label-free immunosensor for detecting the oocyte maturation-inducing hormone 17, 20β-dihydroxy-4-pregnen-3-one (DHP), was developed. A principle of the sensor system was based on differences in electrochemical activity changed by an immunoreaction in the absence and presence of DHP. For preparation of the immunosensor, anti-DHP IgG was immobilized on an Au working electrode modified with a self-assembled monolayer of 3-mercaptopropionic acid. The sensor was immersed into a sample solution containing DHP. DHP was determined by cyclic voltammetry. The immunosensor showed a specific response to DHP, and the oxidation peak current linearly decreased in the range of 7.8–500 pg ml−1 with a correlation coefficient of 0.996. The sensor system was applied to determine the DHP levels in plasma of goldfish and was compared with the DHP levels of the same samples determined using an ELISA as the conventional method. Good correlation was obtained between values determined using both methods in the range of 0.1–7.7 ng ml−1 (correlation coefficient 0.876). These findings suggest that the proposed label-free immunosensor can be used to analyze DHP levels in fish plasma samples.  相似文献   

15.
Specific binding of [3H]17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-DP) to plasma membranes prepared from defolliculated oocytes of rainbow trout (Onchorhynchus mykiss) was identified and characterized. Binding was rapid and reached equilibrium in 30 min. 17α,20β-DP strongly inhibited [3H] 17α,20β-DP binding in a competitive manner. Scatchard analysis revealed two different binding sites: a high affinity binding site with a Kd of 18 nM and a Bmax of 0.2 pmoles/mg protein; and a low affinity binding site with a Kd of 0.5 μM and a Bmax of 1 pmoles/mg protein. This binding activity was successfully solubilized with n-heptyl-β-D-thioglucoside. [3H]17α,20β-DP binding to solubilized preparations reached equilibrium in 1h, and was competitively inhibited with 17α,20β-DP and 17α,20β,21-trihydroxy-4-pregnen-3-one. However, Scatchard analysis showed a single binding site with a Kd of 0.3 μM. The reason for the disappearance of the high affinity binding site in solubilized preparations remains unclear. These results demonstrate that a specific binding site for 17α,20β-DP exists in the plasma membrane of rainbow trout oocytes.
Résumé Une liaison spécifique de le [3H]17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-DP), avec des membranes plasmiques d'ovocytes défollicularisés de truite arc-en-ciel (Onchorhynchus mykiss), a été identifiée et caractérisée. Sa cinétique est rapide et atteint son équilibre en 30 minutes. Le 17α,20β-DP inhibe fortement, et de manière compétitive, la liaison de la [3H] 17α,20β-DP. Une étude de Scatchard a mis en évidence deux sites diffŕents de liaison: un site de forte affinité, de Kd 18 nM et de Bmax 0,2 pmoles/mg de protéine; et un site de faible affinité, de Kd 0,5 μM et de Bmax 1 pmoles/mg de protéine. L'activité de liaison a été solubilisée, avec succés, par le n-heptyl-β-D-thioglucoside. Dans la fraction soluble, la liaison de le [3H]17α,20β-DP atteint un équilibre en 1h.; et elle est complétement inhibiée par la 17α,20β-DP et le 17α,20β,21-trihydroxy-4-pregnen-3-one. Cependant, une étude de Scatchard ne permet de déceler qu'un seul site de liaison, de Kd 0,3 μM. La disparition du site de liaison de forte affinité dans la fraction soluble reste inexpliquée. Ces résultats démontrent l'existence d'un site spécifique de liaison du 17α,20β-DP dans les membranes plasmiques des ovocytes de truite arc-en-ciel.
  相似文献   

16.
Ovarian steroidogenesis during final oocyte maturation (FOM) in the spotted seatrout (Cynoscion nebulosus) was investigated by incubating ovarian fragments with tritiated pregnenolone, followed by chromatographic separation of the radioactive products. The major tritiated steroid produced during FOM comigrated with 17α,20β,21-trihydroxy-4-pregnen-3-one (20β-dihydro-11-deoxycortisol, 20β-S) on HPLC and TLC. Only minor amounts of radioactive material coeluted with 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-P), 11-deoxycorticosterone (DOC), estradiol-17β and testosterone standards in the HPLC system. Additional chromatography by TLC confirmed the presence of radioactive estradiol-17β and testosterone but not 17α,20β-P and DOC. All the ovarian steroids producedin vitro during FOM were assayed for their ability to induce germinal vesicle breakdown (GVBD) of spotted seatrout oocytes. Twenty grams of ovarian tissue were incubated with human chorionic gonadotropin and exogenous pregnenolone. The steroidal products were purified by HPLC and TLC. Most of the maturation-inducing activity was confined to steroidal material which comigrated in these systems with 20β-S. This material was active at a concentration of 1 ng steroid/ml medium in the GVBD assay. Smaller amounts of material which coeluted with 11-deoxycortisol, DOC, 17α,20β-P and several minor unidentified fractions induced GVBD at concentrations of 10 ng steroid(s)/ml. The structure-activity relationships of authentic steroids in inducing GVBD of spotted seatrout oocytes was investigated. Hydroxylation at the 17α, 20β or 21 positions increased potency to induce GVBD. Steroids with multiple hydroxyl groups at the 17α and 20β positions (17α, 20β-P) and at the 17α, 20β, and 21 positions (20β-S) had maximum biological activity in the GVBD bioassay. The results suggest that 20β-S is a major maturation-inducing steroid in spotted seatrout.  相似文献   

17.
Changes in 17-estradiol (E2), estrone (E1), testosterone (T), 11-ketotestosterone (11KT), and 17,20-dihydroxy-4-pregnen-3-one (17,20-P) levels were correlated to changes in gonadosomatic index (GSI), vitellogenin concentration (Vg), ovarian and testicular histology during the annual reproductive cycle of the red porgy, Pagrus pagrus. The production of E2, E1, T and 17,20-P was confirmed by analysis of the steroidogenic activity of ovaries. In females, the average concentration of E2 was lower than 2 ng ml–1. E2 values first increased significantly at the stage of endogenous vitellogenesis and remained high during exogenous vitellogenesis. E1 levels were lower values than E2 (less than 300 pg ml–1), but they increased at the beginning of exogenous vitellogenesis. Estrogens concentrations followed similar pattern to Vg and were significantly correlated. Mean levels of T were mostly lower than 1 ng ml–1. They followed a pattern similar to that of E2 except for a further increase observed at the stage of final maturation. T and E2 levels were significantly correlated. The concentration of 11KT did not change significantly. The levels of 17,20-P ranged between 0.22 and 1.22 ng ml–1 but changes were not related to gametogenesis. In males, the concentrations of T and 11KT fluctuated significantly during the sexual maturity stages, showing a similar pattern and were significantly correlated to GSI changes. T levels increased during spermiogenesis and spermiation stages to reach about 3 ng ml–1. 11KT levels stayed about half those of T. The levels of estrogens showed no significant changes. Level of 17,20-P showed no significant variation related to male maturity. Results are discussed in relation to changes in plasma steroid levels during gametogenesis of other multiple spawner species.  相似文献   

18.
Female greenback flounder Rhombosolea tapirina were treated with either des Gly10 [D-Ala6] LHRH ethylamide (LHRH-a) at 50 or 100 pg/kg intraperitoneal injection (ipi), LHRH-a cholesterol pellet (LHRH-a pellet) 100 μg/kg implanted intraperitoneally, or human chorionic gonadotropin (hCG) 1,000 IU/kg ipi. Treatment with hCG, LHRH-a (50 μg/kg) ipi and LHRH-a pellet increased the total number of ovulations above control levels. LHRH-a (100 μg/kg) ipi was not consistently more effective than the control and both LHRH-a (50 μg/kg) ipi and LHRH-a pellet induced more ovulations than LHRH-a (100 μg/kg) ipi. Of those fish that ovulated, most ovulated more than twice, and most ovulations occurred at daily intervals. Oocyte diameters increased and oocyte stage advanced significantly in response to all exogenous hormone treatments. This was accompanied by increases in plasma and ovarian levels of 17β-estradiol (E2, and in most cases, plasma and ovarian levels of testosterone (T). Plasma and ovarian levels of 17,20β-dihydroxy-4-pregnen-3-one (17,20βP) were not consistently elevated in association with reproductive events.  相似文献   

19.
Chalcalburnus tarichi is an endemic cyprinid species living in the Lake Van basin, in eastern Anatolia, Turkey. The present study was undertaken to determine which hormones induce oocyte maturation in C. tarichi. The levels of 17α,20β,21-trihydroxyprogesterone (20β-S), progesterone (P), 17α-hydroxyprogesterone (17α-HOP), 11-deoxycortisol (11-DOC), and 17α-hydroxy-20β-dihydroprogesterone (17,20β-P) were measured in fish caught from Lake Van and the Karasu River, and injected with human chorionic hormone (hCG) (1,000 and 1,500 IU/kg). Oocytes of fish caught from the lake were also incubated in vitro with different doses (50, 200, and 1,000 ng/ml) of 20β-S, 17α-HOP, 11-DOC, and 17,20β-P. 11-DOC was found to be the most effective hormone among those measured for inducing oocyte maturation in vivo and in vitro. 17,20β-P could not be determined in the plasma of any fish in vivo (P < 0.05). 1,000 IU/kg dose of hCG given by injection caused a statistically significant increase in all plasma hormone levels (P < 0.05). It was found that there was a significant decrease in the P level only at 1,500 IU/kg dose of hCG injected (P < 0.05), while the level of other hormones increased at this dose (P < 0.05). It was also determined that all the hormones were effective in germinal vesicle breakdown (GVBD) in in vitro oocyte culture (P < 0.05). However, 11-DOC was found to be the most effective hormone in GVBD at a dose of 200 ng/ml (70% GVBD). In conclusion, 11-DOC synthesized during final oocyte maturation in C. tarichi was found to be a potent inducer of GVBD, which shows that 11-DOC may be described as an oocyte maturation steroid in this species.  相似文献   

20.
Pituitary gonadotropins (GTHs) are of primary importance in triggering oocyte growth and maturation. However, the actions of GTHs are not direct, but are mediated by the ovarian production of steroidal mediators of oocyte growth (estradiol-17β) and maturation (maturation-inducing hormone, MIH; 17α,20β-dihydroxy-4-pregnen-3-one, 17α,20β-DP in salmonid fishes; 17α,20β,21-trihydroxy-4-pregnen-3-one, 20β-S in sciaenid fishes). It is established that production of estradiol-17β and 17α,20β-DP by salmonid ovarian follicles occurs via the interaction of two cell layers, the thecal and granulosa cell layers (two-cell type model). A distinct shift in the salmonid steroidogenesis from estradiol-17β to 17α,20β-DP occurs in the ovarian follicle layer immediately prior to oocyte maturation. It is possible that this shift is a consequence of dramatic changes in the expression of the genes encoding various steroidogenic enzymes. As an initial step to address this question, we have isolated and characterized the cDNAs encoding a number of ovarian steroidogenic enzymes including the rainbow trout cholesterol side-chain cleavage cytochrome P-450, 3β-hydroxysteroid dehydrogenase (HSD), 17α-hydroxylase/17,20 lyase cytochrome P-450, aromatase cytochrome P-450 cDNAS as well as the pig 20β-HSD cDNA. Estradiol-17β stimulates the hepatic synthesis and secretion of a yolk precursor, vitellogenin. Vitellogenin is then transported to the ovary where it is selectively taken up into the oocyte by a receptor-mediated process involving specific cell-surface receptors. Estradiol-17β was also shown to induce the synthesis of egg membrane proteins in the liver. The maturation-inducing action of 17α,20β-DP and 20β-S is through the binding to the oocyte plasma membrane. This initial MIH-surface interaction is followed by the formation of the major mediator of MIH, maturation-promoting factor (MPF). We have purified MPF from mature oocytes of carp. Carp MPF consists of two components: the homolog of the cdc2+ gene product of fission yeast (p34cdc2) and cyclin B. The cdc2 kinase protein is present in immature oocytes as well as in oocytes induced to mature by 17α,20β-DP treatment, while cyclin B proteins can be detected only in mature oocytes. Addition of bacterially expressed goldfish cyclin B to the extracts of immature goldfish oocytes induced MPF activation. These results suggest that the appearance of cyclin B protein is a crucial step for 17α,20β-DP-induced oocyte maturation in fish.  相似文献   

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