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1.
Three commercially available fatty acid enrichment emulsions (DC Selco, DC DHA Selco and DC Super Selco) were used to enrich Artemia nauplii fed to seahorse, Hippocampus sp. fry. The emulsions varied in their n-3 highly unsaturated fatty acid (HUFA) composition. Total n-3 HUFA content ranged from 200 to 450mgg-1 between the three emulsions while levels of eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) ranged between 47–220 and 80–190mgg-1, respectively. Survival and growth of seahorses at the end of the 30 day growth trial were greater in treatments receiving enriched Artemia. Seahorses receiving Artemia enriched with DC DHA Selco and DC Super Selco showed significantly (p < 0.05) greater mean survival (71.6 ± 6.0% and 78.3 ± 6.0%, respectively) than those receiving unenriched Artemia (48.3 ± 6.0%). Mean standard length was also significantly greater (p < 0.05) in fry fed DC DHA Selco and DC Super Selco enriched Artemia (20.2 ± 0.3 and 19.7 ± 0.3mm, respectively) compared to those fed unenriched Artemia (18.1 ± 0.3mm). The results show that dietary n-3 HUFA are essential for optimal growth and survival of Hippocampus sp. and, based on the fatty acid compositions of the enriched Artemia used in this study, indicate that the level of dietary DHA supporting optimal growth and survival is greater than 9.3mgDHAg-1 dry weight.  相似文献   

2.
Turbot fry (10–20 mm) and juveniles (85–110 mm) were transferred directly from 16.0–16.5 C to 1.0 C, 2.5 C, 5.5 C or 8.0 C seawater. The fry were more sensitive to cold water than juveniles. The fry survived for 1 week at 8.0 C but not at 5.5 C, whereas juveniles survived at 5.5 C but not at 2.5 C. Transfer of juveniles to 1.0 C and 2.5 C seawater caused a high mortality, a marked increase in plasma Cl- concentration, decrease in muscle water content, and hyperglycaemia. Acclimation to 5.5 C (juveniles) or 8.0 C (fry and juveniles) markedly reduced the sensitivity to 1.0 C exposure.  相似文献   

3.
Effective non-bicarbonate buffering capacity (or buffer value) was measured in white muscle of yellow perch (Perca flavescens) by titrations with mineral acid and base in a carbon-dioxide free, closed system. Yellow perch were collected at three month intervals throughout 1983 from an acidic lake (pH 4.6) and two alkaline lakes (pH 7.8) in northern Wisconsin. Buffering capacity was also determined for white muscle of perch kept in the laboratory under different regimes of temperature and ration. The mean buffering capacity of white muscle from yellow perch taken directly from natural environments ranged from 40.7 ± 3.1 (SD) slykes in March of 1983 to 53.7 ± 2.8 (SD) slykes in July of that year. These changes in buffering capacity were strongly correlated with water temperature. Egg production and thirty-day laboratory starvation produced significant decreases in buffering capacity and increases in the water content of yellow perch muscle. Fed perch in the laboratory had a temperature dependent buffering capacity similar to field caught fish. Buffering capacity of white muscle did not differ between yellow perch from acidic and alkaline lakes. Investigators using buffering capacity as a gauge of species differences in metabolic potential, should be wary of seasonal and reproductive factors that might alter their conclusions.  相似文献   

4.
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5.
An 8-week feeding trial was conducted in a recycling water system at 28±1°C to investigate carbohydrate to lipid ratio (CHO:L ratio) in African catfish Clarias gariepinus (12.32±0.04g). Five isonitrogenous (40% crude protein) and isoenergetic (20kJg–1 gross energy (GE)) fishmeal based diets with varying carbohydrate to lipid (CHO:L g/g) ratios of 0.74, 1.13, 1.66, 2.47 and 3.42 for diets 1–5, were tested, respectively. The diets containing a fixed protein to energy ratio (P:E ratio) of 20-mg proteinkJ–1 GE were fed to triplicate groups of 20 fish (per 30-L tank). Fish were fed 5% of their body weight per day adjusted fortnightly. Diet 1, containing 14% carbohydrate and 21% lipids with a CHO:L ratio of 0.74 produced the poorest (P<0.05) growth rates, feed and protein efficiency. Increasing carbohydrate content in the diets to 27% concomitant with a reduction in lipid content to 16% with a CHO:L ration of 1.66 of diet 3 significantly improved (P<0.05) growth rates, feed and protein efficiency. A further increase in dietary carbohydrate up to 38% and a decrease in lipids levels to 11% with a CHO:L ratio ranging from 1.66 to 3.42 (diet 3 – 5) did not significantly improve the fish performance. Apparent net protein utilisation (ANPU) of fish fed diet 4 was higher (P<0.05) than for diets 1–3 but did not differ from diet 5. Higher lipid deposition (P<0.05) in whole body and liver were observed with decreasing dietary CHO:L ratios as increasing lipid levels. Whole body protein and liver glycogen content, digestive enzyme activities (protease and lipase) and histological examination of intestine and liver of fish fed varying CHO:L diets did not show any discernible changes among the dietary treatments. However intestinal -amylase activity increased (P<0.05) with increasing dietary carbohydrate levels. This study revealed that African catfish can perform equally well on diets containing carbohydrate ranging from 27 to 38% of the diet, with lipid content ranging from 16 to 11% or at CHO:Lg/g ratio of 1.7–3.4.  相似文献   

6.
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   

7.
The ingestion of an inert feed as a sole food source was investigated in larval silver sea bream (Sparus sarba) fed an alginate-based microparticulate diet. Using the auto-fluorescent properties of pigments associated with the alginate base, ingestion and gut content were investigated over a 6 h experimental period in fed and unfed larvae. By extracting and measuring chlorophyll a (Chl a) and phaeopigment content of feeding larval fish and relating this to standardized Chl a and phaeopigment content of the diet, relative to diet weight, it was determined that individual fed 7-day old larvae had a maximum gut content of 1.05±0.09 g diet while 14-day old fed fish had a maximum gut content of 3.17±0.90 g diet. On average, the gut content of 14-day old fish was 2.89 times greater than the gut content of 7-day old fish. The dry weight of larval sea bream increased from 43±4.2 g at day 7 to 134.3±20.4 g at day 14 indicating that growth of fish fed this inert feed was substantial. Gut pigment dynamics suggested that Chl a was degraded to phaeopigments by 7-day but not 14-day old larvae and the individual gut dietary content varied considerably in 14-day old fish. The maximum Chl a and phaeopigment content in larval sea bream was 0.4 ng ind–1 and 0.55 ng ind–1 for 7-day old fish and 1.54 ng ind–1 and 2.81 ng ind–1 for 14-day old fish respectively. The present method may potentially allow simple and direct assessment of larval fish feed ingestion in both an experimental and commercial setting.  相似文献   

8.
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   

9.
Atlantic salmon (Salmo salar L) postsmolts weighing 150 ± 53 g were exposed to 14–15 mg l–1 TA-N (total ammonia-N) in sea water in 1 m3 tanks for 24h. Blood samples were then taken A) immediately after the fish were netted from the exposure tanks and stunned by a blow to the head; B) 2–20 min after the fish were transferred to 15 l of an anaesthetic solution of metomidate in ammonia-free sea water; or C) 2–20 min after the fish were transferred to 15 l of ammonia-free sea water. Plasma TA-N level was 18% lower in the anaesthetised fish compared to in the fish sampled directly from the exposure tanks (p 0.05), and accordingly 16% lower in the fish transferred to pure sea water although this difference was not significant (p = 0.07). Plasma glucose level was higher in the fish transferred to pure sea water than in the fish receiving the two other treatments (p 0.05), but plasma urea, osmolality, Na+, Cl–, Ca2+ or Mg2+ levels did not vary significantly between the different treatments. Plasma TA-N level increased with time in the fish in the metomidate solution (p 0.02).  相似文献   

10.
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   

11.
In order to assess the possibilities of utilizing drainage effluents (salinity range 5.0–12.5), fish culture experiments were carried out. Experiments on polyculture using cow dung (24 000 kg ha–1 y–1) as pond fertilizer were conducted at five different salinity levels (0.3–8.5). Studies have revealed that carp perform well in salinities up to 7.5 and reasonably high fish production has been obtained. Even though the ponds had a high trophic status, higher salinities ( > 7.5) appear to repress fish growth probably due to low dissolved oxygen (DO), high BOD and high NH4-N. Experiments on monoculture of common carp (Cyprinus carpio) conducted at two different salinity levels (0.3–0.9 and 6.0–7.0) using four different organic fertilizers (cow dung at 24 000 kg and 20 000 kg, poultry at 1500 kg, duck at 6000 kg and sheep/goat at 1500 kg ha–1 y–1) have revealed the highest fish growth to be in poultry-treated ponds, followed in decreasing order by duck and sheep/goat wastes. Similar trends in fish production were observed both in fresh- and salt-water ponds. However, fish production was lower in ponds having higher salinities ( > 7.5). Nevertheless, these studies indicated that inland saline waters can be utilized for fish culture. With minor modifications in the existing technology of fish culture in stagnant freshwater fish ponds, animal wastes could be used to fertilize brackishwater fish ponds.  相似文献   

12.
Salinity influence on the early stages of the African catfish   总被引：1，自引：0，他引：1  
Experiments were conducted to determine the effect of various incubation salinities on the hatching and survival of eggs and hatched fry respectively of the African catfish (Clarias gariepinus). The optimal salinity for the hatching of the eggs ranged from 0–5. Above 5, hatching was significantly low and no hatching occurred at 8 incubation salinity. Median lethal times (LT50) for fry hatched in 0, 2 and 4 incubation salinities, when abruptly transferred to 10 were 59, 49.5 and 50 h respectively. Similarly, LT50 for fry hatched in 0, 2 and 4 incubation salinities, and abruptly transferred to 12 salinity were 17, 22 and 12.50 h respectively. Increase in incubation salinity of the eggs did not seem to enhance the salinity tolerance of the hatched fry.The gradual (stepwise) increase in salinity of 1 per day of the catfish fry hatched in various incubation salinities (0, 1, 2, 3, 4, 5 and 6) had median lethal salinity values of 8, 8, 8, 10, 10, 11 and 11 respectively. © Rapid Science Ltd. 1998  相似文献   

13.
Theca and granulosa layers were removed from ovarian follicles of mature Atlantic salmon (Salmo salar) and were separately incubated under sterile conditions with and without a partially purified salmon gonadotrophin preparation (GTH). Aliquots of the incubation media were removed at intervals and analysed for the steroids 17, 20-dihydroxy-4-pregnen-3-one (1720P), 17-hydroxyprogesterone, progesterone, androstenedione, testosterone and oestradiol. The biosynthesis of C19 and C21 steroids was very largely restricted to the thecal tissue and was markedly stimulated in the presence of GTH. Androstenedione (max 65 ng/ml) and testosterone (max 14 ng/ml) were released from the earliest stages of incubation whereas the release of 17-hydroxyprogesterone (max 51 ng/ml) and progesterone (max 5.5 ng/ml) commenced only after a lengthy induction period. A trace (1.0 ng/ml) of 1720P was produced by the theca in the presence of GTH but oestradiol was not detected. The granulosa preparations released levels of 17-hydroxyprogesterone and androstenedione only marginally above the detection limits (ca 0.7 ng/ml) and there was little stimulation of output with GTH. Oestradiol (max 4 ng/ml) was released only in the presence of GTH. 1720P, progesterone and testosterone were not detected as products of this tissue. These results, together with those derived earlier from incubations of complete follicles support the view that the synthesis of 1720P is essentially a two-cell process in which 17-hydroxyprogesterone produced in the theca is subject to the action of steroid 20-hydroxysteroid dehydrogenase in the granulosa. The temporal pattern of release of steroids in these and earlier experiments is considered in relation to mechanisms of steroid biosynthesis and to their possible roles in oocyte final maturation.  相似文献   

14.
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   

15.
The present study investigated the relationships between egg viability and ovarian fluid composition, egg physiology and egg metabolism in lake trout, Salmo trutta lacustris, to obtain biomarkers for egg quality determination. The ovarian fluid pH, protein levels and activities of aspartate aminotransferase and -d-glucuronidase were significantly correlated with egg viability expressed as the number of eyed stage embryos. Regression models demonstrated that an ovarian fluid pH between 8.44 and 8.57, protein levels below 235.56 mg 100 ml–1ovarian fluid, aspartate aminotransferase activity below 31.65 m min–1 l–1ovarian fluid and -d-glucuronidase activity below 8.62 m min–1 l–1 ovarian fluid characterized egg batches with high viability (80%).The increase in the egg wet weight during water hardening was also significantly correlated with the number of eyed stage embryos, and egg batches with high egg viability (80%) increased in wet weight by 13% during water hardening.From the investigated metabolic parameters the number of eyed stage embryos was significantly correlated with activities of NADP-dependent isocitrate dehydrogenase (egg viability 80% at 2.07 nM min–1 mg–1 protein) and NAD-dependent malate dehydrogenase (egg viability 80% at 47.25 nM min–1 mg–1 protein), with the respiration rate (egg viability 80% at 8.71 nM min–1 mg–1 protein), with the ratio of NADH to NAD levels (egg viability 80% 0.872), with the levels of free, non-esterified fatty acids (egg viability 80% 72.34 g mg–1 protein), and the ratio of non esterified to esterified fatty acids (egg viability 80% at 0.749). Also, subjective and visual control methods were described to distinguish between batches with viable and non viable eggs.  相似文献   

16.
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   

17.
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   

18.
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   

19.
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   

20.
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   

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