首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 109 毫秒
1.
Thein vitro secretion of 17,20-dihydroxy-4-pregnen-3-one 20-sulphate (17,20-P-sulphate) and the free steroid 17,20-dihydroxy-4-pregnen-3-one (17,20-P), by rainbow trout (Oncorhynchus mykiss) gonads, in response to gonadotropin (GTH) I and GTH II, were studied during the final stages of sexual maturation. Substantial amounts of 17,20-P-sulphate were produced, by both mature ovaries and testes, indicating considerable 20-hydroxysteroid sulphotransferase (20-HST) activity within these tissues. In the post-ovulatory ovary the level of 17,20-P-sulphate (36.6 ng ml–1) greatly exceeded that of 17,20-P (8.59 ng ml–1). The amount of 17,20-P-sulphate produced in incubations of both mature ovary and testes was unaffected by either GTH I or GTH II treatment at physiological concentrations up to 100 ng ml–1. Similarly, incubations of maturing ovary and testes, treated with GTH I or GTH II, in the presence of added 17,20-P at 100 ng ml–1 of medium, produced levels of 17,20-P-sulphate that were similar to those of the controls. In incubations of mature ovarian follicles at the stages of germinal vesicle breakdown and preovulation, both GTHs significantly stimulated secretion of 17,20-P, although GTH II was always more potent than GTH I. GTH II significantly elevated the levels of 17,20-P in testicular incubations from mature males more than 4-fold relative to GTH I and controls, which did not differ from one another.In conclusion, 20-HST, the enzyme responsible for the sulphate conjugation of 17,20-P, was found to be active in the ovaries and testes of rainbow troutin vitro. However, the levels of this enzyme do not appear to be regulated by either GTH I or GTH II.  相似文献   

2.
Salmon pituitary glands contain two structurally distinct -subunit proteins (1 and 2) of glycoprotein hormones: the 2-subunit is common to all salmon gonadotropins (GTH I and GTH II), whereas the 1-subunit is present in only some GTH I molecules. GTH I is predominant in the pituitary gland and plasma during gametogenesis of salmon, but the roles of the 2 GTHs in gametogenesis remain unclear. To understand the roles of GTH I, it is important to clarify patterns of 1- and 2-subunit production with sexual maturity. Thus, we produced antisera that recognized the 1- or 2-subunit, and then immunohistochemically examined the production sites of these subunits in the trout pituitary gland during ovarian development. In all pituitary glands examined, the immunoreactivity of both the 1- and 2-subunits was strong in the GTH II-producing cells, although salmon GTH II, both 1- and II-subunits, has not been detected. However, GTH I-producing cells showed a less dense immunoreactivity for 1- and 2-subunits, whereas the I-subunit was abundant. On the other hand, TSH cells, reacted with 2 but not with 1.  相似文献   

3.
The plasma concentrations of fourteen ovarian steroids were measured in postvitellogenic African catfish,Clarias gariepinus, which had been injected with pimozide and LHRHa. Postvitellogenesis persisted for at least four hours after pimozide and LHRHa administration. During this stage a limited rise in the plasma gonadotropin (GTH) level was accompanied by an increase in the testosterone concentration. The estradiol level was high and remained high except for a passing drop during the stage of germinal vesicle migration. At the stage of germinal vesicle migration a strong increase in the plasma GTH level coincided with a maximum in the testosterone concentration and a concomitant increase in the levels of 17,20-dihydroxy-4-pregnen-3-one and of five 5-reduced pregnanes. During germinal vesicle breakdown the GTH concentration remained high, the plasma level of 17-hydroxyprogesterone tended to increase, and the levels of 5-pregnane-3, 17-diol-20-one, 5-pregnane-3,17,20-triol and 5-pregnane-3,17,20-triol reached a maximum. At pre-ovulation the GTH concentration did not change, and peak levels were reached of 17,20-dihydroxy-4-pregnen-3-one and 5-pregnane-3,6,17-triol-20-one. Shortly after ovulation the GTH concentration slightly decreased together with a sharp decline in the concentrations of 17,20-dihydroxy-4-pregnen-3-one and the 5-reduced steroids, with the exception of 5-pregnane-3,17,20-triol, 5-pregnane-3,6,17,20-tetrol and 5-dihydrotestosterone. The plasma concentrations of androstenedione, estrone, etiocholanolone and 5-androstane-3,17-diol showed marginal fluctuations during oocyte maturation and ovulation. Apart from 17,20-dihydroxy-4-pregnen-3-one, the 5-reduced pregnanes might be candidates for the function of oocyte maturation inducing hormone inC. gariepinus.  相似文献   

4.
The cDNAs encoding the glycoprotein hormone -subunit (GP) and the gonadotropin II-subunit (GTH II) were cloned from the pituitary gland of the African catfish, Clarias gariepinus. Using RNase protection analysis, we studied the steady-state mRNA levels of GP as well as GTH II in the pituitary gland of adult male catfish. Castration of adult male catfish resulted in a significant decrease of GTH II mRNA levels, whereas there was no change in the GP mRNA levels. Treatment of intact males with a single dose of 11-ketotestosterone (11-KT) resulted in dose-dependent increases in mRNA levels of both GP and GTH II. We conclude that 11-KT, a prominent, non-aromatizable teleost androgen, has a stimulatory effect on the pituitary mRNA levels of GP and GTH II of adult male fish.  相似文献   

5.
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   

6.
In order to specify the timing of some changes in ovarian steroid production during the transition from vitellogenesis to ovulation, plasma hormones levels andin vivo andin vitro responses of the ovary to salmon gonadotropin (s-GtH) or dibutyryl-cyclic adenosine mono-phosphate (db-cAMP) were recorded in relationship with the state of germinal vesicle migration in the oocyte.In vivo, a small, but significant, increase of plasma 17-hydroxy-20-dihydroprogesterone (17, 20-OH-P) level was detected earlier (at the subperipheral germinal vesicle stage) than the increase of GtH level (detectable at the peripheral germinal vesicle stage) and the decline of oestradiol-17 (E2–17) (also detectable at the peripheral germinal vesicle stage). Negative correlations were established between E2–17 levels and GtH (=–0.53) or 17,20-OH-P (=–0,43) levels while a positive correlation occurred between 17,20-OH-P and GtH levels (=+0,54).In vivo no action of GtH on the decline of E2–17 levels was detected GtH did not stimulate 17,20-OH-P production, within 72h, in females at the end of vitellogenesis stage. It had significant effect in females at other stages closer to ovulation, but the pattern of responses changed according to the stage.In vitro db-cAMP like GtH was able to stimulate 17,20-OH-P output from ovarian follicles. The greatest response was observed at the later stage. (GVBD). Testosterone output was also increased by GtH, but the lowest response was observed at the later stage (GVBD). Androstenedione output was lower than testosterone output.In vitro, a small but significant decline of E2–17 output was induced by GtH. We conclude that substantial changes occur during the very last stages prior to ovulation, both in the steroidogenic potential of the ovary and in the ovarian sensitivity to GtH. 20-oxydoreductase is probably progressively induced during GV migration when GtH basal levels are increasing but still relatively low. Without minimizing the role of discrete pulses of GtH on this induction, we could expect synergic actions of other hormones. Thus a high testosterone/oestradiol ratio in the follicle environment favours 17,20-OH-P secretion.  相似文献   

7.
As part of a series of experiments concerning a possible pheromonal function of steroids and steroid glucuronides excreted by the sex organs of the African catfish,Clarias gariepinus, qualitative and quantitative studies, using GCMS, were carried out to examine the presence of the steroids, that can be synthesized by the ovary during oocyte maturation and ovulation, and of the corresponding steroid glucuronides, in the fluid surrounding the eggs in the ovarian cavity shortly after ovulation.Full mass spectra were obtained of 5-pregnane-3,17-diol-20-one, 5-pregnane-3,17,20-triol, 5-pregnane-3,6,17-triol-20-one, 5-pregnane-3,6,17,20-tetrol, 5-androstane-3,17-diol and 5-androstane-3,17-diol-11-one. After selected ion monitoring the following steroids could be detected by the presence of at least two characteristic ions at the expected retention time: 5-pregnane-3, 17,20-triol, etiocholanolone, 5-dihydrotestosterone, 5-androstane-3,11-diol-17-one, testosterone and estradiol. After treatment with -glucuronidase the following steroids could be determined in a similar way: 5-pregnane-3,17-diol-20-one, 5-pregnane-3,17,20-triol, 5-pregnane-3,17,20-triol, 5-pregnane-3,6,17-triol-20-one, 5-pregnane,3,6,17,20-tetrol, 5-androstane-3,17-diol, etiocholanolone, 5-dihydrotestosterone, testosterone and estradiol.The free steroids 5-pregnane-3,6,17,20-tetrol and 5-pregnane-3,6,17-triol-20-one and the steroid glucuronides of testosterone, 5-dihydrotestosterone and estradiol appeared to be the most abundant of these compounds. The results indicate that very polar steroids and steroid glucuronides, synthesized in the ovary, can be excreted via the ovarian fluid shortly before and during oviposition, and possibly function as sex attractants, inducing reproductive behaviour in male conspecifics.  相似文献   

8.
Maturation-inducing steroid (MIS) in the Indian female catfish,Clarias batrachus, was purified and characterized from the incubation medium in which fully grown but immature folliculated oocytes were incubated with salmon gonadotropin (SG-G100) for 36 h. Maturation-inducing (MI) activity of residues obtained at various steps of extraction and purification was assessed byin vitro germinal vesicle breakdown (GVBD) assay using folliculated oocytes ofC. batrachus. The post incubation medium was extracted with diethyl ether. The ether phase was partitioned using 50% methanol plus n-hexane. The methanol phase which had MI activity was fractionated into 7 fractions using reverse-phase high-performance liquid chromatography. Of these 7 fractions, fraction 3 was found to be active in having MI ability and identified as 17 ,20-dihydroxy-4-pregnen-3-one (17,20-diOHprog). The authenticity of 17,20-diOHprog as the major follicular mediator of gonadotropin-induced oocyte maturation was further confirmed by thin-layer chromatography (TLC) in which fraction 3 was run along with authentic 17,20-diOHprog standard. This investigation gives a direct evidence that 17,20-diOHprog is the major naturally occurring MIS in Indian female catfish,C. batrachus.  相似文献   

9.
The objective of this study was to investigate the effects of sex steroids on spermiation in protandrous male black porgy, Acanthopagrus schlegeli. Experiments on common carp (Cyprinus carpio) were also conducted for comparison. Fifty male black porgy were divided into 5 groups and injected with a superactive analogue of mammalian luteinizing hormone releasing hormone (LHRH-A), 17,20,21-trihydroxy-4-pregnen-3-one (20-S), 17,20-dihydroxy-4-pregnen-3-one (17,20-DHP), 11-ketotestosterone (11-KT) or saline. The dosage of the sex steroids given on days 0, 2, 4 and 6 was 330, 330, 990 and 1980 µg kg-1 body weight, respectively. Milt volume and sperm concentrations were measured on days 0, 2, 4, 6, 8 and 10. Similar treatments were also conducted in 45 male common carp. Milt volume was significantly increased in black porgy after treatment with 20-S and 17,20-DHP; 17,20-DHP had stimulatory effects on spermiation at a lower dose (900 µg kg-1 body weight, p < 0.05) as compared to 20-S (1980 µg kg-1 body weight, p < 0.01). In the common carp, milt volume was also increased after treatment with LHRH-A and 17,20-DHP but not with 20-S. 17,20-DHP stimulated spermiation at a lower dose in common carp (330 µg kg-1 body weight) than in black porgy (990 µg kg-1 body weight). However, 11-KT did not stimulate spermiation in black porgy or common carp. The concentrations of plasma 11-KT could immediately reflect to the administration of exogenous 11-KT in black porgy.  相似文献   

10.
Changes in ovarian steroidogenesis accompanying oocyte maturation and ovulation were studied in the African catfish,Clarias gariepinus. Laboratory-reared females with postvitellogenic ovaries were treated with pimozide and LHRH-analogue. The plasma gonadotropin levels were determined by means of a homologous radioimmunoassay, the condition of the ovaries was studied by histological examination of the follicles, and the steroidogenetic capacity of the ovaries was analyzed byin vitro incubation of tissue fragments for 3 h with [3H]-pregnenolone and [3H]androstenedione as precursors. Data were collected at regular intervals between 0 and 16 h after pimozide-LHRH analogue administration.Until 4 h after the beginning of the experiments the plasma gonadotropin levels did not rise above 25 ng/ml, the ovaries remained in the stage of postvitellogenesis, and testosterone was the main end product of steroidogenesis. Four hours later the gonadotropin concentration in the blood had risen to more than 150 ng/ml, and the ovaries had entered the stage of germinal vesicle migration. At the same time steroidogenesis shifted towards the production of 17,20-dihydroxy-4-pregnen-3-one, 5-pregnane-3, 17-diol-20-one, 5-pregnane-3,6,17-triol-20-one, 5-pregnane-3,17,20-triol and 5-pregnane-3,6,17,20-tetrol. During the subsequent stage of germinal vesicle breakdown the plasma gonadotropin level remained high, and the synthesis of the C21-steroids showed a further increase. Simultaneously, the production of some C19-steroid glucuronides was enhanced. The preovulation and especially the postovulation stages were accompanied by a gradual decrease in steroidogenic capacity of the ovaries, even though the plasma gonadotropin level remained high. It is concluded that the prematuration surge of gonadotropin influences the activity of enzymes involved in steroidogenesis, leading to a reduced C17,20-lyase and to an augmented activity of the enzymes 20-hydroxysteroid dehydrogenase (HSD), 5-reductase, 3-HSD, 6-hydroxylase and UDP-glucuronosyltransferase. During ovulation the activity of all steroidogenic enzymes, including such key enzymes as 3-HSD and 17-hydroxylase, gradually decreases.Not only 17,20-dihydroxy-4-pregnen-3-one, but also the 5-reduced pregnanes may be involved in inducing oocyte maturation and/or ovulation. The very polar triol and tetrol products may function, together with the steroid glucuronides as sex pheromones.A preliminary account of these results was presented at the XIII Conference of European Comparative Endocrinologists, Belgrade, September 7–12, 1986  相似文献   

11.
17-estradiol, 17-20-dihydroxy-4-pregnen-3-one (17-20-P), and testosterone levels were measured in plasma samples obtained from vitellogenic coho salmon (Oncorhynchus kisutch) before and 32 days after injection of the aromatase inhibitor Fadrozole (AI). Plasma 17-estradiol levels decreased significantly 6 h after injection in all AI treated fish. The higher the dose the longer the maintenance of low plasma 17-estradiol levels. Inversely, plasma 17-20-P increased significantly 6 h after injection in all AI treated fish, and the higher the dose the longer the maintenance of high plasma 17-20-P levels. At 48 h after injection plasma testosterone levels were significantly higher in the AI treated groups. The oocyte maturation index showed that multiple injections with AI retarded oocyte development. Besides, oocyte diameter and GSI were lower in the same group, which presented high incidence of atresia of vitellogenic oocytes. The ovarian follicles and brain of the fish which received multiple injections secreted less 17-estradiol, in vitro. These findings suggest that aromatase inhibitors such as Fadrozole may have a potential as a tool to regulate sexual development in salmon.  相似文献   

12.
The purpose of this work was to study the turnover of a, andtocopherol (TOH) in Atlantic salmon (Salmo salar, L.). Fish induplicate tanks were fed a diet containing 150 mg kg-1-TOH and 100 mg kg-1 each of and TOHadded as tocopheryl acetates. After fillet TOH concentrations had adjustedto the dietary supplementation levels, samples were taken from fish that hadbeen deprived of feed for 100 h, and from fish that had been fed regularlyuntil sampling. The retained levels of tocopherols in plasma correspondedgrossly with their biological activities, as found in experiments withmammals (::100: 20:3). The plasma concentrationsof -, and TOH amounted to 65, 44 and 15%,respectively, in unfed compared to fed fish. Very low density lipoprotein(VLDL), appeared to contain a greater fraction of plasma -TOH than ofplasma TOH. The mitochondrial fraction of liver, but not that of darkmuscle, was highly enriched in -TOH, and less in andTOH. The concentration ratios in liver and bile indicate that, and to some extent, TOH are excreted in the bile at a higherrate than -TOH. The data fit the hypothesis that Atlantic salmonliver contains a tocopherol binding protein with higher affinity for-TOH than for the other tocopherol homologues. This appears toprevent excretion of -TOH in the bile, and stimulate incorporation of-TOH in VLDL for subsequent secretion into the blood stream. As aconsequence, -TOH is retained in the body to a greater extent than and -TOH.  相似文献   

13.
The relative effectiveness of estradiol-17, androgens, corticosteroids, progesterone and other pregnene derivatives on germinal vesicle breakdown (GVBD) was investigatedin vitro using folliculated oocytes of three carps,Labeo rohita, Cirrhinus mrigala, andCatla catla. In all three species progesterone and 17-hydroxyprogesterone could induce GVBD but relatively 17,20-dihydroxyprogesterone was consistently found to be the most potent maturation-inducing steroid. Both estradiol-17 and testosterone were ineffective in inducing GVBD. Androsterone and dehydroepiandrosterone were found to be effective inC. catla at all the concentrations used. Deoxycorticosterone (DOC), hydrocortisone (HC) and cortisone were effective inducer of GVBD inC. catla whereas inL. rohita andC. mrigala only cortisone was found to be effective. All 5-reduced pregnenes were effective in inducing GVBD inL. rohita but inC. catla, only 5-pregnane-17-01-3,20-dione and 5-pregnane-3,17,20-triol and inC. mrigala, 5-pregnane-3-ol-20- one could induce oocyte maturation.  相似文献   

14.
Three experimental approaches were chosen to study the question if the progestin 17-hydroxy-20-dihydroprogesterone (1720OHP) is synthesised in testes of young Oncorhynchus mykiss, in which the absence of spermatozoa was verified histologically: first, in order to detect 20-hydroxysteroid dehydrogenase activity (20HSD), testes homogenates were incubated with 3H-labeled 17OHP.Metabolites were analysed by TLC, HPLC, and repeated crystallization to constant isotope ratios. One of the metabolites was identified as 1720OHP-3H, indicating that already immature testes contain 20HSD activity and are able to produce 20-reduced steroids. Second, 1720OHP was quantified by radioimmunoassay in incubates of testes fragments. The sensitivity of the gonads to gonadotropin II (GtH II) became evident when comparing incubations in the absence and presence of GtH II. Third, plasma levels of 1720OHP were significantly higher in animals injected with partially purified salmon gonadotropin, compared to controls. Thus, for the first time, it could be shown that 20HSD is present in testicular cells other than spermatozoa. Furthermore, 1720OHP is indeed secreted at a very early stage of testicular development; 1720OHP secretion is also responsive to GtH II. Future studies will have to show if the functions of this progestin include the stimulation of spermatogenesis.  相似文献   

15.
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   

16.
Full-grown immature Clarias batrachus oocytes respond in vitro to exogenous 17,20-dihydroxy-4-preg-nen-3-one ( 17,20-DP) by undergoing germinal vesicle breakdown (GVBD). Cytosolic extract (CE) prepared from 17,20-DP-induced oocytes has been shown to produce similar effect when microinjected into unstimulated immature oocytes of the same fish. A dose of 50 nl is enough to cause 100% GVBD after 4 h. Maturation-promoting factor was investigated from 17,20-DP-induced, immature and cycloheximide treated oocytes incubated in presence of [35S] methionine. When the proteins were extracted and analyzed on SDS-PAGE, two prominent bands corresponding to molecular weight 34- and 46-kDa were detected in the CE of mature oocytes. However, labelling of [35S] methionine was observed mainly in the region of 46 kDa protein band indicating de novo synthesis of this particular protein during l7,20-DP-induction. Further, immunoblotting study by using rabbit anti-cyclin B1 antibody has clearly demonstrated that the protein which is newly synthesized is highly homologous to Xenopus cyclin B1 and goldfish cyclin B.  相似文献   

17.
This paper presents the relationship between egg quality and egg biochemical composition of cultured and wild Japanese eel, Anguilla japonica. Eggs were obtained by artificialinduction of maturation. Fertilization and hatching rates were used as characteristics of egg quality. Egg quality characteristics showed large variation; fertilization rate, 0–96; hatching rate, 0–84%. The biochemical composition also showed a large variation. There was no marked relationship between egg quality and fatty acid contents of eggs, except for n-6 highly unsaturated fatty acids (HUFA). Both the fertilization and hatching ratesincreased proportionally withincreases of the -tocopherol g(-Toc) contentin eggs. A more significant correlation was found between the amount of -Toc relative to the amount of HUFA and egg quality. The results of this study show that the egg quality of Japanese eel is affected by the –Toc level, andin particular, the ratio of -Toc to HUFAin the eggs. Abbreviations: BHT – butylhydroxytoluene; EFA – essential fatty acids; FAME – fatty acid methyl esters; HPLC – high performance liquid chromatography; HUFA – highly unsaturated fatty acids; NADH – nicotinamide adenine dinucleotide; NADPH - nicotinamide adenine dinucleotide phosphate; ROS – reactive oxygen species; -Toc –-tocopherol.  相似文献   

18.
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   

19.
Gonad and plasma samples were taken from blue cod captured throughout the reproductive cycle, gonad condition was assessed, and plasma levels of 17-hydroxyprogesterone (17OHP), 17,20-dihydroxy-4-pregnen-3-one (17,20P), testosterone (T), 17-estradiol (E2) and estrone (E1) were measured by radioimmunoassay. It was confirmed that spawning occurred over an extended period in late winter and spring, with individual fish being involved in multiple spawning events. Plasma levels of T were bimodal in both sexes with peaks (maximum of 6.0 ng.ml–1) occurring 2 months prior to, and also during the early part of the spawning period. 17,20P was elevated in males (2.1 ng.ml–1) in mid-spermatogenesis coinciding with the first T peak (4.9 ng.m.–1). 17,20P was detectable but not significantly elevated (0.6–1.2 ng.ml–1) at any sample time in females. E2 was elevated in mature females (1.0 ng.ml–1) early in the spawning period but remained at assay detection limits (0.3 ng.ml–1) at all other sample times. Neither 17OHP nor E1 were detectable in the plasma of either sex. It is suggested that bimodal increases in sex steroids prior to spawning may be a feature of species with rapid recrudescence.  相似文献   

20.
Rainbow trout ovarian follicles were incubated in vitro with tritiated 17,20-dihydroxy-4-pregnen-3-one (17,20-P; maturation-inducing steroid). Within 18–24 h, 56–66% had been converted to tritiated 17,20-dihydroxy-4-pregnen-3-one 20-sulfate (identification confirmed by HPLC) and 27% had been taken up (absorbed) by the follicles. Addition of 125 ng of cold (non-tritiated) 17,20-P to the incubations caused a decrease in the percentage of [3H]-17,20-P which was sulfated (56% 10%) and an increase in the percentage that was taken up (27% 57%). Seven steroids were tested for their effectiveness in decreasing the sulfation and increasing the uptake of tritiated [3H]-17,20-P. The order of effectiveness was in both cases the same: 17,20-P > cortisol > 11-deoxycortisol > 17,20,21-trihydroxy-4-pregnen-3-one > 17-hydroxy-4-pregnene-3,20-dione > 17-estradiol > testosterone. This indicated that the processes of sulfation and uptake of [3H]-17,20-P were related to each other and led to the hypothesis that, when cold 17,20-P is added to the medium, it reduces the proportion of [3H]-17,20-P which is sulfated and thus allows more free [3H]-17,20-P to enter the ovarian follicles. This hypothesis was supported by the finding that each ovarian follicle had the capacity in vitro to sulfate only ca. 2 ng of [3H]-17,20-P per 18h but a capacity to take up > 500 ng per 18h.Gonadotropin I, Gonadotropin II, forskolin and phorbol-12-myristate-13-acetate (which all have an affect on steroid biosynthesis) did not affect the amount of 17,20-P which was sulfated. Sulfating activity was localized in the thecal cell layer of the follicle. The yolk fraction was shown to be responsible for absorbing the [3H]-17,20-P.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号