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1.
The effect of cortisol on the in vitro metabolism of [3H]17-hydroxyprogesterone ([3H]17OHP) was studied during embryonic development of Arctic charr (Salvelinus alpinus) and rainbow trout (Oncorhynchus mykiss). In the absence of cortisol, rainbow trout embryos metabolized [3H]17OHP largely to androstenedione (A4) and androstenetrione (11-KA) with a minor conversion to 17,20ß-dihydroxy-4-pregnen-3-one (17,20P). In the presence of cortisol, this biosynthesis was inhibited. On the other hand, cortisol had no apparent inhibitory effect on the nature of metabolism of [3H]17OHP by Arctic charr embryos. In these embryos [3H]17OHP was metabolized mainly to 17,20P with a minor conversion to A4 and without the formation of 11-KA that was seen in rainbow trout.When incubated in the presence of [3H]cortisol both Arctic charr and rainbow trout embryos produced 11ß-hydroxyandrostenedione (11ß-OHA) as the major metabolite, with a minor conversion to an unknown steroid. The catabolism of the cortisol by salmonid embryos may reflect the ability of the embryo to inactivate or detoxify cortisol to protect itself from the adverse effects of this biologically potent steroid hormone The study indicates the existence of species-specific differences in the nature of metabolism of [3H]17OHP and the inhibitory effect of cortisol on this metabolism.  相似文献   

2.
Two year old black porgy (Acanthopagrus schlegeli) fed a diet containing 4.0 mg kg–1 of estradiol-17 (E2) for 5 months had significantly lower GSI than the control group during the spawning season. E2 suppressed testicular development, spermiation and plasma testosterone (T) and 11-ketotestosterone (11-KT) and stimulated ovarian development, vitellogenesis and sex reversal. Spermiation in the control group occurred in January and February with the concentrations of 1.08–1.36 × 1010 sperm ml–1 of milt. Higher plasma T and 11-KT, but lower E2 levels were detected in the spermiating fish (control group). Higher plasma E2 levels were detected in the sex reversing black porgy during the pre-spawning season. A sharp rise in plasma 11-KT and a drop in T levels were detected in spermiating fish (control group) from January to February. Plasma 11-KT levels correlated with the testicular development and spermiation. The data suggest that E2 plays an important role in controlling the sex reversal of black porgy.to whom correspondence should be addressed.  相似文献   

3.
In fish, sex steroids initiate and/or accelerate the maturation of the brain-pituitary-gonad axis. In order to obtain information on the steroid milieu during the pubertal development of male African catfish, we have monitored the conversion of [3H]-pregnenolone and [3H]-androstenedione by testis and [3H]-pregnenolone by interrenal tissue fragmentsin vitro. Pubertal development occurs between two and six months of age. Testicular development proceeds through four main stages that are characterised histologically by the presence of spermatogonia (stage I), spermatogonia and spermatocytes (stage II), spermatogonia, spermatocytes and spermatids (stage III), and all germ cells including spermatozoa (stage IV). 11β-Hydroxyandrostenedione and cortisol were the main products of testes and interrenal tissue, respectively, in all stages of the pubertal development; a change in the steroidogenic pattern was not observed during this period. The interrenal tissue displayed no significant conversion of [3H]-pregnenolone to 11-oxygenated androgens. Blood plasma was analyzed for the presence of five androgens; testosterone, 11β-hydroxytestosterone, 11β-hydroxyandrostenedione, androstenetrione, and 11-ketotestosterone. 11-Ketotestosterone was the quantitatively dominating androgen in the circulation at all stages of development, which was more pronounced in stages III and IV. The obvious differences between thein vitro andin vivo results, namely 11β-hydroxyandrostenedione being the main testicular productvs. 11-ketotestosterone dominating in the blood, may indicate that 11β-hydroxyandrostenedione is converted to 11-ketotestosterone at extratesticular sites.  相似文献   

4.
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   

5.
Cytosol from brook trout ovarian follicles (stages 1–3) was photoaffinity (PA) labelled using synthetic progestin 17,21-dimethyl-19-nor-pregn-4,9-diene-3,20-dione ([3H]R5020). The covalently bound cytosol protein had a relative mass of 501,000 Mr following Sephacryl S-300 column chromatography. The zona radiata membrane fraction from brook trout oocytes which had gone through the first phase of meiotic maturation (stages 6–7) was isolated by ultracentrifugation of the whole oocytes. The zona radiata solubilized protein presumably from the oocyte membrane was also PA labelled and found to give a peak at 355,000 Mr. The SDS PAGE of the cytosol and zona radiata PA labelled protein gave very similar subunits indicating that the membrane protein and the cytosol protein, both of which bind the maturation inducing steroid (MIS) 17,20-dihydroxy-4-pregnen-3-one (17,20-DHP), have similar subunit structures. The isolated zona radiata protein showed cooperativity of binding to [3H]17,20-DHP and PA labelling to [3H]R5020. The association constant (Ka) was 2.0×107M–1 and maximum binding capacity (Nmax) 427 fmoles/mg protein with MIS [3H]17,20-DHP.No evidence for nuclear binding of MIS [3H]17,20-DHP or PA labelling of [3H]R5020 to nuclei was observed. The nuclei were isolated from stages 1 and 3 fresh ovarian follicles of brook trout. The experimental evidence presented demonstrates the presence of MIS 17,20-DHP receptor-like protein from the zona radiata membranes by PA labelling in brook trout oocytes during final stages of maturation.  相似文献   

6.
The aims of the present study were to characterize sperm quality and to quantify seasonal changes in sexual hormone (testosterone [T], 11-ketotestosterone [11-KT] and 17,20β-dihydroxypregn-4-en-3-one [17,20β-P]) levels in male brill (Scophthalmus rhombus) plasma, as well as to test a more intensive sampling strategy to establish relationships between sex steroid levels and sperm production parameters. Sperm concentration ranged from 0.5 to 3.1 × 109 spermatozoa mL?1, and changes in sperm quality parameters depending on sampling date were observed. Plasma sexual steroid levels remained high and changed in parallel during the spawning season and afterwards decreased to very low levels in summer. The analysis of annual changes of 11-KT and T ratios suggests that 11-KT can be the main circulating androgen for stimulating spermatogenesis in S. rhombus and that T could be involved in the beginning of spermatogenesis through the positive feedback on brain-pituitary-gonad axis. Finally, daily 11-KT and T levels showed similar patterns of variation in males sampled, whereas 17,20β-P amounts showed somewhat opposite trends. These differences could be related with the different role of androgens and progestin during the spermatogenesis.  相似文献   

7.
Ovarian follicles taken from sexually maturing rainbow trout at the mid-vitellogenic stage of ovarian development were incubated in vitro in the presence or absence of melatonin or somatostatin-14 (SRIF-14) to determine whether there is evidence of a direct action of these factors on gonadal steroidogenesis in fishes. The steroidogenic capacity of the ovarian follicles was assessed by measuring testosterone (T) and 17-estradiol (E2) release into the incubation medium, and by examining the steroid metabolites produced following incubation of follicles with radiolabelled steroid precursors.Melatonin appears to elicit a biphasic effect on steroidogenesis by in vitro rainbow trout ovarian follicles; at a concentration of 1 × 10–3 M, melatonin stimulated basal T and E2 production, but at a concentration of 1 × 10–2 M there was an inhibition of basal and sGtH-stimulated T and E2 Melatonin may act to reduce the activity of specific steroidogenic enzymes, since there was evidence of melatonin at 1 × 10–2 M enhancing the accumulation of [3H]17-hydroxyprogesterone in the medium following incubation with [3H]pregnenolone, possibly suggesting the inhibition of C17,20-lyase activity. In contrast, SRIF-14, used at concentrations of 1 × 10–8 M and 1 × 10–6 M, had no effect on basal or sGtH-stimulated E2 or T production by ovarian follicles, incubated in vitro.  相似文献   

8.
The in vitro basal and salmon gonadotropin (sGTH)-stimulated steroidogenic capacity of rainbow trout follicles was examined at four stages [early (EV)-, mid (MV)- and peak-vitellogenic (PV), and pre-ovulatory, post-vitellogenic (PO)] of gonadal recrudescence using radioimmunoassays (RIAs) to measure 17-estradiol (E2) and testosterone (T) production. In addition, follicles were incubated in the presence of [3H]pregnenolone ([3H]P5) and the radiolabelled steroid metabolites produced were separated using high performance liquid chromatography (HPLC). Peak basal and sGTH-stimulated E2 and T production was found in PV stage follicles and lowest in PO stage follicles, and there were marked differences in the HPLC profiles of steroid metabolites. For EV stage follicles the major metabolite eluted as a peak that co-eluted with the androstenedione (A4) and 17-hydroxyprogesterone (17-OHP) standards. A smaller peak that co-eluted with 11-hydroxyandrostenedione (11-OHA4) and very small peaks co-eluting with 20-dihydroprogesterone (20-DHP) and E2 were also seen. MV and PV stage follicles produced predominantly E2, together with a small combined A4 + 17-DHP peak, traces of 11-OHA4 and two peaks that did not co-elute with any of the reference standards. The PO stage follicles produced only 17, 20-dihydroxy-4-pregnene-3-one (17,20-P).In addition, the effects of cortisol and triiodothyronine (T3) on steroidogeneis were investigated in PV and PO stage ovarian follicles. For PV stage follicles, cortisol at 100 ng ml–1 in the incubation medium significantly suppressed both basal and sGtH- stimulated T and E2 production relative to control treatments. T3 at 10 ng ml–1 in the medium had no significant effect on either basal or sGtH-stimulated T or E2 production compared to the controls, nor did it have any beneficial effect over the suppressive effect of cortisol. PO phase follicles taken 1 to 2 weeks prior to anticipated spawning had very low E2 and T production, and there was no effect of cortisol or T3, alone or in combination, on E2 or T production. For PV stage follicles incubated in the presence of [3H]P5, cortisol suppressed T and E2 production, but did not block the steroid pathway at any specific level; T3 had no apparent affect on the metabolism of [3H]P5. The PO stage follicles produced little or no E2; the major metabolite was 17,20-P. Cortisol and T3 had no apparent effect on either basal or sGtH-stimulated 17,20-P production by the follicles at this stage of maturation.  相似文献   

9.
The presence of 17,20-dihydroxy-4-pregnen-3-one (17,20-DHP) oocyte receptor activity has been demonstrated in brook troutSalvelinus fontinalis. Scatchard analyses of the cytosol fraction during various terminal stages of oocyte maturation gave a high equilibrium association constant (Ka) value of 1.394±0.669 108M–1 (n=7) and low maximum binding capacities (Nmax). The association kinetics of the receptor was second order k+1=2.292×106M–1 sec–1. The dissociation rate constant ka was 1.502×10–2 sec–1 for the first order dissociation reaction. The Ka=1.526×108M–1, when it was determined from k+1/k–1 a value close to that found from the Scatchard analysis. Competition studies showed the following binding affinities testosterone > 17-HP > 17,20-DHP > Promegestone > progesterone > estradiol > pregnenolone; cortisol showed no competitive inhibition. Cytosolic extracts when pre-equilibrated with various labelled steroids and eluted from a Sephacryl S-300 column gave multiple specific binding peaks. On sucrose density gradient centrifugation specific binding was observed at 3.05 S in cytosol containing 0.15M sodium chloride buffer. The receptor lost binding activity when incubated with various proteases, but DNase and RNase had no effect. Blood plasma without heparin at (110) dilution also bound [3H]17,20-DHP, Ka was 8.04×107 M–1.The nuclear pellet extract (750×g) gave very little specific binding activity even at high radiolabelled steroid concentrations and a linear Scatchard plot was not obtained. Nevertheless the nuclear extract, after dextran-charcoal treatment, pre-equilibrated with [3H]17,20-DHP, bound specifically to DNA cellulose, and cytosol from the same oocytes also bound to DNA cellulose under similar conditions. Although specific binding to DNA cellulose was obtained the salt concentrations at which the steroid-receptor complex elution took place was not reproducible in both nuclear extracts and cytosol samples. Also binding activity was extremely small compared to the total cytosolic binding. The nuclear extract when pre-equilibrated with high concentrations (20 nM) of the labelled steroid and then chromatographed on Sephacryl S-300 column gave a specific binding peak which was similar to that of the cytosolic preparation.The receptor levels in cytosol decreased progressively during final maturation (Stages 1–7). There is preliminary evidence for the presence of 17,20-DHP receptor activity in cytosol of landlocked Atlantic salmonSalmo salar ouananiche, and rainbow troutSalmo gairdneri. The zona radiata fraction from late stages oocyes 5, 6, and 7 in brook and rainbow trout oocytes were isolated by ultracentrifugation; from this fraction a protein was characterized which covalently bound [3H]R5020 after photoaffinity labelling. The same protein also bound [3H]17,20-DHP after solubilization in Brig 35 buffer. The SDS gel electrophoresis subunit composition of the above protein was similar to the cytosol counterpart binding [3H]17,20-DHP, although the molecular weights were different. The blood sample [3H]R5020 binding component subunit composition was different from that of the membrane extracted protein. These results demonstrate the presence of 17,20-DHP receptor activity in the cytosol and zona radiata membranes of the oocytes during final maturation.A. Maneckjee is presently NSERC postgraduate scholar at MSRL and Ph.D. candidate at Department of Biochemistry, Memorial University of Newfoundland.  相似文献   

10.
The immunosuppressive effects of steroid hormones were evaluated as the response against implanted steroid hormones, cortisol (F), testosterone (T), estradiol-17 (E2), and 11- ketotestosterone (11-KT), in juvenile rainbow trout. In long term experiments (5 weeks), fish were given a single intraperitoneal implant of F or T. A clear suppressive effect of plasma IgM levels with F and T was not necessarily obtained, although mucus IgM levels were reduced corresponding to the elevated plasma steroid hormone levels. In short term experiments (1 week), intraperitoneal implantation of T, 11-KT and E2 suppressed plasma and mucus IgM levels, although the effects were not dose-dependent. When administered through diet, F and T caused a suppression of plasma IgM levels; F administration at both high and low dosages caused a significant decrease in plasma IgM levels, while only a high dose of T caused the suppression. These results suggest that sex steroid hormones, as well as F, have immunosuppressive functions in rainbow trout.  相似文献   

11.
The binding characteristics of 17,20,21-trihydroxy-4-pregnen-3-one (20-S) to plasma membranes prepared from the testes and sperm of spotted seatrout (Cynoscion nebulosus) were investigated using a filtration method to retain the bound 20-S. A single class of high affinity (Kd = 17.9 nM), low capacity (Bmax = 0.072 nM g-1 testes) binding sites was identified by saturation and Scatchard analyses on testicular membranes of spermiating spotted seatrout. A corresponding receptor (Kd = 22.17 nM, Bmax = 0.00261 nM ml-1 milt) was also detected in spermatozoan membrane preparations. The rates of 20-S association and dissociation were rapid, both had Thalfs of less than 1 min. Competition studies indicated that the receptor was highly specific for 20-S. 17,20-dihydroxy-4-pregnen-3-one, which had the highest affinity of the other steroids tested, had a relative binding affinity (RBA) of 14.3%. Progesterone, 11-deoxycortisol and testosterone competed with an order of magnitude less affinity (RBA's of 7.4, 1.8 and 1.1%, respectively). Estradiol displayed low affinity for the receptor (RBA = 0.4%) and cortisol did not cause any displacement at 1000-fold excess concentration. Specific 20-S receptor binding was detected in plasma membranes from testes of both spermiating and non-spermiating seatrout and on spermatozoa. Prolonged incubation of testicular fragments from a spermiating fish with gonadotropin (15 IU ml-1 human chorionic gonadotropin) or forskolin (10 µM) caused a 2–3 fold increase in membrane receptor binding. Previous studies have shown that gonadotropin-induced upregulation of the 20-S plasma membrane receptor in seatrout ovaries is required for the oocytes to become responsive to 20-S and undergo final maturation. The existence of a 20-S membrane receptor on sperm and its upregulation in the testes by gonadotropin raises the possibility that final maturation of spermatozoa in male seatrout may be regulated by a similar mechanism.  相似文献   

12.
The involvement of androgens during sex differentiation period was investigated in the pejerrey Odontesthes bonariensis, by classic biochemical studies and gonadal histology. We studied in particular whether the enzyme activities involved in 11-oxygenated androgen production were active in a gonadal/peritoneum complex (GPC) of very small larvae exposed to masculinizing temperatures previous to morphological sex differentiation (5 weeks post-hatching). The GPC was incubated with 17-hydroxyprogesterone (3H-17P), and the presence of 11-KT as major metabolite in early gonads undergoing masculine pathway after temperature treatment exposure is reported. 11-KT was identified by thin-layer chromatography and high-pressure liquid chromatography. The present results show that 11-KT is produced at very early stages of testis development in pejerrey, being this androgen one of the main mediators of the masculinization induced by temperature treatment at the gonad level.  相似文献   

13.
ABSTRACT:   In order to clarify the roles of androgen and gonadotropin-releasing hormone (GnRH) on gonadotropin (GTH; luteinizing hormone [LH] and follicle stimulating hormone [FSH]) synthesis, effects of castration and implantation of GnRH analog (GnRHa) or 11-ketotestosterone (11-KT) on expression of GTH subunit, α-glycoprotein subunit (αGSU), FSHβ, and LHβ genes, during the early spermatogenic stage in male red seabream Pagrus major were examined. Male red seabream underwent castration or sham-operation and were subsequently implanted with cholesterol pellets containing GnRHa, silicone capsules filled with 11-KT, or blank capsules (control). FSHβ mRNA levels increased due to castration, and it was reversed by treatment with 11-KT. 11-ketotestosterone treatment also decreased FSHβ mRNA levels in sham-operated fish. These results suggest that 11-KT acts on the pituitary to suppress FSH synthesis in male red seabream. On the other hand, neither castration nor replacement of 11-KT in castrated fish had effects on LHβ mRNA levels, whereas 11-KT treatment had slightly but significantly decreased LHβ mRNA in sham-operated fish. αGSU mRNA levels were not changed by castration or 11-KT treatment in both sham-operated and castrated fish. Meanwhile, treatment with GnRHa significantly decreased FSHβ mRNA levels in sham-operated fish, but not in castrated fish. This suggests that GnRHa may down-regulate expression of FSHβ mRNA through the production of 11-KT in testis. LHβ and αGSU mRNA levels in sham-operated fish, but not in castrated fish, were significantly elevated by treatment with GnRHa.  相似文献   

14.
The control of 11-ketotestosterone (11-KT) biosynthesis and its physiological roles were examined in female Japanese eel (Anguilla japonica) and New Zealand longfinned eel (Anguilla dieffenbachii). 11-KT was detected in serum of female eels of both species. Among various tissues from Japanese eel, the ovary had the greatest capacity to synthesize 11-KT in vitro. In addition, the oocyte diameters of eels treated with 11-KT had increased significantly. Furthermore, these oocytes were found to have an increased number of oil droplets. These findings suggest that 11-KT in female eels may be mostly of ovarian origin and that this androgen appears to play an important role in controlling pre-vitellogenic oocyte growth.  相似文献   

15.
Our previous studies on the effect of stress on pubertal development in carp have shown that repeated temperature changes caused an increase in cortisol levels and a retardation of the first waves of spermatogenesis. Identical effects, accompanied by a decrease in 11-ketotestosterone (11KT) plasma levels and the gonadosomatic index (GSI) were induced by cortisol administration via cortisol containing food pellets. The decrease in plasma 11KT is caused by a direct effect of cortisol on the steroid producing capacity of the testis, independent of luteinizing hormone (LH) levels. However, the mechanism through which cortisol interferes with testicular steroidogenesis is unknown. In the present study, we showed that in vitro physiological levels of cortisol can inhibit the conversion of 11β-hydroxyandrostenedione (OHA) into androstenetrione (OA), which is the precursor of 11KT, possibly by competing for the enzyme 11β-hydroxysteroid dehydrogenase (11β-HSD). The same mechanism may occur in vivo. However, our results demonstrate that an elevation of plasma cortisol levels during acute cortisol treatment did not result in lower plasma levels of OA and 11KT, but we did observe an accumulation of OHA. We suggest that the previously observed decrease in 11-oxygenated androgens, as an effect of long-term cortisol treatment, is caused by a retardation of testicular development. This results in a lower steroid synthesizing capacity of the testis as a whole. Although the in vitro observed cortisol inhibition of the conversion of OHA into 11KT plays a role in the accumulation of OHA, it apparently has no effect on the final 11KT plasma concentration. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

16.
The initial appearance and the development of Leydig cells (LCs), the sites of steroid hormone production in the testis, were investigated ultrastructurally during testicular differentiation in the Japanese eel, Anguilla japonica. In addition, the effects of a single injection of human chorionic gonadotropin (HCG; 5 IU g body weight-1) on histological changes of the testes and serum 11-ketotestosterone (11-KT) were examined at various stages (15–18, 20–23, 26–29, 32–35, 38–41 and 46–50 cm body length (BL)) of testicular differentiation. Testicular differentiation was morphologically characterized by the development of loose connective tissue on the medial side in animals 18–29 cm in BL. Ultrastructurally, LCs were first identified in the loose connective tissue of the testis of the 23 cm fish. In the testes of fish over 32 cm, clusters of LCs were distributed throughout the interstitial region accompanying the increase in number of spermatogonia. In fish larger than 32 cm, spermatogenesis was induced by administration of HCG; serum 11-KT levels were also raised. On the other hand, there was no effect on spermatogenesis or serum 11-KT levels in fish less than 29 cm, or in the controls. These result suggests that morphological differentiation of LCs occurs in testis of the 23 cm eel, and subsequently, the testes of eels of BL more than 32 cm acquire the capability to produce steroid hormones.  相似文献   

17.
Fish spermatogenesis, from spermatogonial stem-cell renewal to sperm maturation, is controlled by the sex steroid hormones. Mitotic divisions of spermatogonia can be categorized by spermatogonial stem cell renewal and spermatogonial proliferation. Spermatogonial renewal is regulated by estradiol-17β (E2; the natural estrogen in vertebrates), and spermatogonial proliferation toward meiosis is promoted by 11-ketotestosterone (11-KT), the main androgen in teleost. The action of E2 and 11-KT is mediated by other factors produced by Sertoli cells; E2 is mediated by spermatogonial stem-cell renewal factor and 11-KT is mediated by spermatogenesis preventing substance and activin B. Although 11-KT also induce meiosis and spermiogenesis, the control mechanisms of these processe are not clear. After spermiogenesis, immature spermatozoa undergo sperm maturation. Sperm maturation is regulated by 17α,20β-dihydroxy-4-pregnen-3-one (DHP), which is progestin in teleost. The DHP acts directly on spermatozoa to active the carbonic anhydrase existed in the spermatozoa. This enzymatic activation causes an increase in the seminal plasma pH, enabling spermatozoa to motile.  相似文献   

18.
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19.
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   

20.
High levels of 11-ketotestosterone (11KT) were found (49 to 160 ng ml–1) in plasma of Siberian sturgeon females during the end of their reproductive cycle. These levels were measured either by specific radioimmunoassay, or both by specific radioimmunoassay and by UV absorption after HPLC (isocratic conditions, 33% methanol, 26% acetonitrile, 41% water). In order to find the origin of 11KT synthesis, ovaries were incubated (30 min and 2h at 20°C) with tritiated 17-hydroxyprogesterone (17OHP) or with tritiated androstenedione (A4). Testosterone (conversion rate from tritiated 17OHP: 4%) and 11-ketotestosterone (conversion rate from tritiated A4: 1.6%) were identified as metabolites of respectively 17OHP and A4 (TLC, HPLC and crystallization). 11-hydroxyandrostenedione (11OHA4) and 11-hydroxytestosterone (11OHT) were suggested to be intermediate metabolites. Besides interrenal and blood cells were incubated respectively with tritiated cortisol and tritiated A4. 11OHA4 was identified in interrenal incubation (yield from tritiated cortisol: 1.2%). 11KT in interrenal (yield from tritiated cortisol: 0.14%), and 11OHA4 and 11KT in blood cells (yield from tritiated A4: 1.6%), were suspected to be synthesized (TLC, HPLC, acetylation). No significant metabolization of tritiated cortisol could be found in liver. The possible contribution of each of these tissues to high 11KT levels found in plasma is discussed.To whom correspondence should be sent  相似文献   

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