In vitro metabolism of pregnenolone to 7alpha-hydroxypregnenolone by rainbow trout embryos

Gene structure and comparative and phylogenetic analyses of Catla catla CYP1A full-length cDNA and its responsiveness to benzo(a)pyrene and copper sulphate at early developmental stages

In the present study, full-length CYP1A cDNA from Catla catla (Catla) has been identified, and its real-time quantitative reverse transcription PCR (qRT-PCR) expression has been evaluated in different tissues, developmental stages (0, 3, 6, 12 and 24 h and 5, 7 and 9 days post-fertilization) and copper sulphate and benzo(a)pyrene (BaP)-treated 5-day post-fertilization (dpf) larvae (6 to 6.5 mm). Various structural, comparative and phylogenetic analyses of the deduced amino acid sequence revealed that the identified gene of Catla belongs to the CYP1A1 subfamily. Among different tissues of Catla, the highest CYP1A expression was observed in the kidney followed by the liver, muscle, gill, intestine and brain. CYP1A mRNA expression was detected during all the larval developmental stages, including the unfertilized egg with the highest expression on 9 dpf. BaP (3.5 ppb) and copper sulphate (sublethal dose 0.516 ppm) challenge test for 96 h to Catla larvae revealed the highest CYP1A1 expression at 48 h post-challenge. CYP1A1 transcript also showed a concentration-dependent increase in expression following exposure at 1.75 and 3.5 ppb of BaP for 48 h. Its expression profiling indicates that it is functional at early developmental stages. It can also be used to develop a specific biomarker tool for monitoring environmental pollution.

Effect of 17α-hydroxyprogesterone and 17α-hydroxypregnenolone on sperm quality and sperm quantity in male mud spiny lobster (Panulirus polyphagus)

The present study aimed to determine the effect of 17α-hydroxyprogesterone (17α-OHP) and 17α-hydroxypregnenolone (17α-OHPL) on sperm quality and sperm quantity in male mud spiny lobster (Panulirus polyphagus). The mean of sperm quality was increased in 17α-OHP and 17α-OHPL treated hormones. In 17α-OHP injected animals, the mean of sperm quantity of dose 0.01 μg g(-1) b.wt. was increased than 17α-OHPL. Meanwhile, 17α-OHP and 17α-OHPL concentrations were lower when injected with the hormones but 17α-OHP was higher at only day 15 (dose 0.01 and 0.1 μg g(-1) b.wt.). For 17α-OHPL, the hormone was a prohormone in the body of P. polyphagus and only required smaller to increase the sperm quantity. Besides, when the higher dose of 17α-OHPL (0.1 μg g(-1) b.wt.) was used in P. polyphagus, the development of P. polyphagus was inhibited and decreased the sperm quantity and 17α-OHPL concentration in hemolymph was lower. Injection of 17α-OHP in P. polyphagus has increased the sperm quality and quantity for both 17α-OHP dosage of 0.01 and 0.1 μg g(-1) b.wt. However, injection of 17α-OHPL in P. polyphagus has decreased the sperm quantity only, also for both dosage of 0.01 and 0.1 μg g(-1) b.wt. and lower on hormone concentration.

Molecular responses to 17β-estradiol in early life stage salmonids

Environmental estrogens (EE) are ubiquitous in many aquatic environments and biological responses to EEs in early developmental stages of salmonids are poorly understood compared to juvenile and adult stages. Using 17β-estradiol (E2) as a model estrogen, waterborne exposures were conducted on early life stage rainbow trout (Oncorhynchus mykiss; egg, alevin, swim-up fry) and both molecular and physiological endpoints were measured to quantify the effects of E2. To investigate developmental stage-specific effects, laboratory exposures of 1 μg/L E2 were initiated pre-hatching as eyed embryos or post-hatching upon entering the alevin stage. High mortality (∼90%) was observed when E2 exposures were initiated at the eyed embryo stage compared to the alevin stage (∼35% mortality), demonstrating stage-specific sensitivity. Gene expression analyses revealed that vitellogenin was detectable in the liver of swim-up fry, and was highly inducible by 1 μg/L E2 (>200-fold higher levels compared to control animals). Experiments also confirmed the induction of vitellogenin protein levels in protein extracts isolated from head and tail regions of swim-up fry after E2 exposure. These findings suggest that induction of vitellogenin, a well-characterized biomarker for estrogenic exposure, can be informative measured at this early life stage. Several other genes of the reproductive endocrine axis (e.g. estrogen receptors and androgen receptors) exhibited decreased expression levels compared to control animals. In addition, chronic exposure to E2 during the eyed embryo and alevin stages resulted in suppressive effects on growth related genes (growth hormone receptors, insulin-like growth factor 1) as well as premature hatching, suggesting that the somatotropic axis is a key target for E2-mediated developmental and growth disruptions. Combining molecular biomarkers with morphological and physiological changes in early life stage salmonids holds considerable promise for further defining estrogen action during development, and for assessing the impacts of endocrine disrupting chemicals in vivo in teleosts.

The in vitro metabolism of cortisol by ovarian follicles of rainbow trout (Oncorhynchus mykiss): comparison with ovulated oocytes and pre-hatch embryos

Mid-vitellogenic stage rainbow trout (Oncorhynchus mykiss) ovarian follicles (both intact and yolk free (YF)), ovulated oocytes and embryos were co-incubated with [2,4,6,7-3H]cortisol for 18 h to determine the degree and nature of the metabolism and biotransformation of the glucocorticoid. There was evidence of the conversion of cortisol to the less biologically potent glucocorticoid, cortisone, and the formation of glucocorticoid sulphates (both cortisol and cortisone) for all cell and tissue samples, suggesting the presence of 11β-hydroxysteroid dehydrogenase (11β-HSD) and glucocorticoid sulphotransferase (GST) activity at all stages; however, GST activity was particularly marked in both intact and YF ovarian follicles, suggesting an important role of follicles in limiting the exposure of oocyte to maternal cortisol. As there was no evidence of 11β-HSD or GST activity in ovarian fluid, the findings affirm that ovarian follicles (probably the thecal and granulosa cells) provide a barrier against the transfer of cortisol to the oocytes by forming sulphated steroids, whereas ovulated oocytes and early embryos have a more limited capacity to either metabolize or conjugate cortisol and are therefore more vulnerable at the post-ovulatory and early embryonic stages to increases in exposure to the glucocorticoid.

Cytochrome P450 (CYP) in fish

Cytochrome P450 (CYP) enzymes are members of the hemoprotein superfamily, and are involved in the mono-oxygenation reactions of a wide range of endogenous and exogenous compounds in mammals and plants. Characterization of CYP genes in fish has been carried out intensively over the last 20 years. In Japanese pufferfish (Takifugu rubripes), 54 genes encoding P450s have been identified. Across all species of fish, 137 genes encoding P450s have been identified. These genes are classified into 18 CYP families: namely, CYP1, CYP2, CYP3, CYP4, CYP5, CYP7, CYP8, CYP11, CYP17, CYP19, CYP20, CYP21, CYP24, CYP26, CYP27, CYP39, CYP46 and CYP51.We pinpointed eight CYP families: namely, CYP1, CYP2, CYP3, CYP4, CYP11, CYP17, CYP19 and CYP26 in this review because these CYP families are studied in detail. Studies of fish P450s have provided insights into the regulation of P450 genes by environmental stresses including water pollution. In this review, we present an overview of the CYP families in fish.

Effect of glutamate and somatostatin-14 on basal and cAMP-stimulated steroidogenesis by rainbow trout (Oncorhynchus mykiss) ovarian follicles, in vitro

The effects of glutamate and somatostatin-14 (SRIF) on the in vitro basal and cAMP-stimulated steroid production of mid-vitellogenic rainbow trout (Oncorhynchus mykiss) ovarian follicles were investigated. cAMP-stimulation was achieved by the addition of the adenylyl cyclase activator, forskolin (FS), or a membrane permeate cAMP agonist, 8-bromo-cAMP (BA), to the incubation medium. Testosterone (T) and 17beta-estradiol (E(2)) secretion was measured using radioimmunoassay. Solid phase extraction (SPE) was used to measure the relative formation of unconjugated and conjugated steroids, and high performance liquid chromatography (HPLC) was used to examine the steroid metabolites formed from the metabolism of a tritium labelled precursor, pregnenolone (P(5)). The accumulations of T and E(2) in the medium were suppressed in the presence of the glutamate agonists, N-methyl-d,l-aspartate (NMA) or l-glutamic acid (GA), and by the presence of SRIF. The suppression was evident for both basal and cAMP-stimulated steroidogenesis except for T concentrations of GA treatments following basal steroidogenesis, when there were no treatment effects. No significant effects of treatment on conjugated:unconjugated steroid ratios were found. For all treatments E(2) was the major end product steroid synthesized from P(5), and the steroid profiles were similar except for trace amounts of radiolabelled androgens in the medium following cAMP-stimulated steroidogenesis that were not present following basal steroidogenesis. The findings suggest that glutamate and SRIF reduce end point steroid production, possibly by reducing P(5) production. However, since the inhibitory affect was found for basal and cAMP-stimulated steroidogenesis, the response does not appear to be due to the inhibition of cAMP synthesis.

Effects of sub-lethal levels of dichlorodiphenyltrichloroethane and dichlorodiphenyldichloroethylene on in vitro steroid biosynthesis by ovarian follicles or steroid metabolism by embryos of rainbow trout (Oncorhynchus mykiss)

This study examined the possibility that DDT and DDE, at sub-lethal exposure levels, exert direct effects on the biotransformation of gonadal steroids by rainbow trout (Oncorhynchus mykiss) ovarian follicles and embryos. Ovarian follicles were co-incubated with DDT or DDE at 0.01 or 1 mg l-1 to examine effects of the pesticides on basal or cAMP-activated steroidogenesis. Ovarian preparations were incubated with radiolabelled [3H]pregnenolone ([3H]P5), and the tritiated metabolites of [3H]P5 metabolism were separated using high-performance liquid chromatography (HPLC). Testosterone (T) and 17beta-estradiol (E2) production were also measured using radioimmunoassay (RIA). Embryos were either exposed to the pesticides in ovo, or co-incubated in vitro with the pesticides. The effect of the pesticides on embryo steroid biotransformation was examined using a range of radioactively labelled substrates, including [3H]P5, [3H]progesterone ([3H]P4), [3H]T and [3H]E2. At the concentrations used, the pesticides had no significant effect on the relative amounts of unconjugated radiolabelled steroids formed by the biotransformation of [3H]P5 under conditions of basal or cAMP-stimulated ovarian steroidogenesis. However, DDT and DDE appeared to reduce the basal accumulation of androgen as a product of P5 biotransformation by ovarian follicles. Basal or cAMP-stimulated total estrogen production was not affected. In addition, DDT at 1 mg l-1 and DDE at 0.01 mg l-1 significantly increased and decreased cAMP-stimulated T accumulation, respectively. Also DDT at 0.01 mg l-1 and DDE at 1 mg l-1 significantly increased and decreased basal E2 accumulation, respectively. The steroid metabolites synthesized from the different substrates by embryos were essentially similar in both controls and pesticide-exposed groups, and the survival of embryos to hatch was not significantly affected by pesticide exposure, in ovo, with an approximately 90% hatchability in all treatment groups. This study suggests that although DDT and DDE may affect ovarian androgen synthesis under some conditions, under the conditions of the present study, they do not impact on overall rates of gonadal estrogen synthesis. Similarly, the pesticides do not appear to directly affect steroid biotransformation by embryos.

Evidence for 15α- and 7α-hydroxylase activity in gonadal tissue of the early-life stages of sea lampreys, Petromyzon marinus

Gonads of premetamorphosing larval (PML), transforming (TL) and newly metamorphosed (juvenile) sea lampreys (JL) (Petromyzon marinus) were incubated in vitro with tritiated pregnenolone ([(3)H]P(5)), progesterone ([(3)H]P(4)), and androstenedione ([(3)H]A(4)) to identify the major products of steroidogenesis in early developmental stages. Reverse-phase high-performance liquid chromatography, using two mobile phase gradients, was used to separate the radioactive steroid metabolites. 7alpha-Hydroxylase activity was evident, based on the loss of radioactivity from [(3)H]P(5) labelled at position 7, appearing as tritiated water, and on the appearance of radiolabelled 7alpha-hydroxypregnenolone in the incubation medium. In addition, there was evidence of the synthesis of 15alpha-hydroxylated steroids from the three steroid precursors used. For the progestogen precursors, one of the major 15alpha -hydroxylated metabolites synthesized by both testis and ovarian tissue co-eluted with authentic 15alpha-hydroxyprogesterone, and for [(3)H]A(4), the product was predominantly [(3)H]15alpha-hydroxyandrostenedione. Additional polar steroids were produced, some of which co-eluted with authentic 15alpha-hydroxytestosterone and 15alpha-hydroxyestradiol, whereas others could not be correlated with the authentic 15alpha- or 15beta-hydroxylated steroids available. Ovarian tissues from PML and TL developmental stages synthesized several very non-polar compounds, some of which were present as unconjugated compounds, and others only in the conjugated fraction. These molecules had retention times consistent with pregnanes, and their presence in the incubation medium was therefore indicative of the presence of 5alpha-reductase. These metabolites were not present in the incubation medium from testis, or the JL ovary, suggesting that there is no expression of 5alpha-reductase activity in these tissues. Traces of 17beta-estradiol were found in the incubation medium from ovarian tissue incubated with P(5), but not following incubation with P(4) or A(4). Testosterone was not present in the incubation medium from either ovarian or testis fragments incubated with any of the substrates used.

Effect of glutamate on basal steroidogenesis by ovarian follicles of rainbow trout (Oncorhynchus mykiss)

The effects of glutamate on the in vitro basal steroid production of three maturational stages of rainbow trout (Oncorhynchus mykiss) ovarian follicles were investigated. Radioimmunoassays were used to measure the rates of synthesis of testosterone (T) and 17-estradiol (E2). High performance liquid chromatography (HPLC) was used to examine the steroid metabolites produced from a tritium labeled precursor, pregnenolone (P5). The glutamate agonist, N-methyl-d,l-aspartate (NMA) had a dose-dependent suppressive effect on T and E2 synthesis in mid-vitellogenic (MV) follicles, but had no significant effect on early- (EV) and late-vitellogenic (LV) follicles. l-glutamic acid (GA) had a dose-related suppressive effect on T synthesis by MV follicles, suppressing both T and E2 synthesis by LV follicles, but having no effect on EV follicles. HPLC separation of the steroid metabolites synthesized from P5 showed clear evidence of differences in rates of overall steroidogenesis of the three follicular stages, but no effect of either NMA or GA on the nature or the amount of the metabolites produced by the three developmental stages examined. The findings suggest that glutamate may act via a reduction in the production of P5, which is the principal rate-limiting step in the steroidogenic cascade, and not via modulation of steroidogenic enzyme activities.

The role of CYP 1A1 in the in vitro metabolism of pregnenolone by the liver of rainbow trout embryos

The in vitro metabolism of pregnenolone (P5) was investigated using whole liver preparations taken from rainbow trout (Oncorhynchus mykiss) embryos sampled between 55 and 61 days post-fertilization. The intent of the study was to use HPLC techniques to separate and identify the metabolites of hepatic P5 metabolism and identify the enzyme(s) involved. The major metabolite of [3H]P5 catabolism was [3H]7alpha-hydroxypregnenolone ([3H]7alphaOHP5), and the enzyme involved was hypothesized to be a cytochrome P450 (CYP) isozyme. To test that hypothesis, whole liver preparations from embryos were pre-treated with selected CYP inhibitors prior to incubation with [3H]P5 and post-mitochondrial supernatant (PMS) fractions of embryo livers were pre-treated with specific antibodies raised against rainbow trout CYP 1A1 prior to incubation with radiolabelled steroid precursor. Three of the four inhibitors used (Miconazole, Clotimazole, Ketokonazole) and the CYP 1A1 antibodies totally blocked the conversion of [3H]P(5) to [3H]7alphaOHP5, and the fourth, Metyrapone, partially blocked the conversion. These results suggest that CYP 1A1 is the major enzyme involved in hepatic catabolism of P5 by rainbow trout embryos.