Plasma Steroid Concentrations Research Articles

Individual variation and the endocrine regulation of behaviour and physiology in birds: a cellular/molecular perspective.

Investigations of the cellular and molecular mechanisms of physiology and behaviour have generally avoided attempts to explain individual differences. The goal has rather been to discover general processes. However, understanding the causes of individual variation in many phenomena of interest to avian eco-physiologists will require a consideration of such mechanisms. For example, in birds, changes in plasma concentrations of steroid hormones are important in the activation of social behaviours related to reproduction and aggression. Attempts to explain individual variation in these behaviours as a function of variation in plasma hormone concentrations have generally failed. Cellular variables related to the effectiveness of steroid hormone have been useful in some cases. Steroid hormone target sensitivity can be affected by variables such as metabolizing enzyme activity, hormone receptor expression as well as receptor cofactor expression. At present, no general theory has emerged that might provide a clear guidance when trying to explain individual variability in birds or in any other group of vertebrates. One strategy is to learn from studies of large units of intraspecific variation such as population or sex differences to provide ideas about variables that might be important in explaining individual variation. This approach along with the use of newly developed molecular genetic tools represents a promising avenue for avian eco-physiologists to pursue.

What is normal? A characterization of the values and variability in reproductive endpoints of the fathead minnow, Pimephales promelas

Jensen et al. [Jensen, K.M., Korte, J.J., Kahl, M.D., Pasha, M.S., Ankley, G.T., 2001. Aspects of basic reproductive biology and endocrinology in the fathead minnow ( Pimephales promelas). Comp. Biochem. Physiol. C 128, 127–141.] investigated aspects of the normal reproductive biology of the fathead minnow (FHM, P. promelas), and subsequent studies have generated a large amount of additional reproductive data for endpoints such as plasma steroid hormone and vitellogenin concentrations, spawn interval, and secondary sex characteristics (i.e., nuptial tubercle score and fat pad weight). These data were analyzed and fitted with statistical distributions to improve understanding of the variability in normal, unexposed, adult male ( n = 154) and female ( n = 186) FHM. Summary statistics for most endpoints were consistent with results from other more limited studies of FHMs. Male fat pad weight, and in both sexes gonad and liver weights were found to be proportional to body weight. Multiple statistical distributions were found to characterize each endpoint with the exception of spawn interval. Based on one of the largest datasets ever compiled for controlled studies, results presented herein provide a robust point of reference for the quantitative assessment of reproductive processes in the fathead minnow.

Dietary patterns, the Alternate Healthy Eating Index and plasma sex hormone concentrations in postmenopausal women

To evaluate the association between overall diet and sex hormones concentrations, we collected blood from 578 postmenopausal women ages 43 and 69 years in 1989 or 1990. Food intake was measured in 1990 via a food frequency questionnaire. We calculated the Alternate Healthy Eating Index (AHEI), and dietary patterns were identified by factor analysis. The cross-sectional association between diet and estrogens, sex hormone binding globulin (SHBG) were evaluated with linear regression and adjusted for energy and other potential confounders. We found a higher AHEI score was associated with lower concentrations of estradiol, free estradiol, and higher concentrations of SHBG. The prudent pattern, with higher intakes of fruits, vegetables, and whole grains, was not associated with any sex hormones. The Western pattern, which represents higher intakes of red and processed meats, refined grains, sweets and desserts, was associated with a higher level of estradiol and lower concentrations of SHBG. Further adjustment for BMI attenuated these results except for free estradiol (5th vs. 1st quintile = 0.09 vs. 0.11 pg/mL, p for trend = 0.03). In addition, the AHEI was inversely associated with estradiol among those with BMI > 25, and Western pattern with SHBG among those with BMI < 25. In conclusion, we observed inverse associations between the AHEI score and several estrogens, and it was positively associated with plasma levels of SHBG. In contrast, the Western pattern was positively associated with estrogen levels and inversely with SHBG. However, these associations appeared to be largely accounted for by BMI.

Effects of in utero TPTCL Exposure on the Learned Behaviors of Mice after Birth

Takagi, S., Tomonaga, S., Ito, S., Oshima, Y., Honjo, T. and Furuse, M. 2007. Effects of in utero TPTCL exposure on the learned behaviors of mice after birth. J. Appl. Anim. Res., 31: 13–20. The open field test and the elevated plus-maze test were applied to investigate the effects of in utero triphenyltin chloride (TPTCL) exposure on learned behavior in ICR strain mice. During pregnancy mice (8-weeks-old) received daily oral administration of vehicle (corn oil) or TPTCL (0.9 and 9 mg/kg) for a period of up to 18 days. Plasma sex hormone concentrations, body weight and organ weights were not significantly changed and no external malformations were noted after TPTCL exposure in either dams or pups. However, a decrease in the number of animals completing pregnancy and the number of dams rearing pups normally was observed in the 9 mglkg TPTCL group. No behavioral effects of TPTCL treatment were observed in pups or dams in the two tests employed. Measurable levels of TPTCL were found in the brains of dams in the TPTCL dosage group, but not in the brains of their pups. These results indicated that the TPTCL dosages and treatment period used did not influence metabolism and/or learned behaviors in mice. However the possibility is suggested that TPTCL may have adverse effects on normal pregnancy and maternal behavior.

Comparison of estradiol, testosterone, vitellogenin and cathepsin profiles among young adult channel catfish ( Ictalurus punctatus) females from four selectively bred strains

Potential variation in reproductive performance as young broodfish among four selectively bred strains of channel catfish was evaluated by comparing profiles of plasma estradiol, testosterone, and vitellogenin, and activities of cathepsin D, L, and B in follicle-enclosed oocytes during vitellogenesis in 2- to 3-yr-old females. No differences among the four strains were detected for any of the parameters measured. Plasma steroid concentrations demonstrated temporal differences, with testosterone levels peaking in January and estradiol levels peaking in April. Monthly changes in circulating vitellogenin concentrations coincided with oocyte growth. Average oocyte size in May, the typical time of spawning, was smaller (1624 μm) than that considered normal for mature oocytes (approx. 3000 μm) in this species. Furthermore, only 9% of the females in this study spawned, and no significant correlations could be determined between the reproductive indices and spawning success. Activities of cathepsin D, L, and B were also similar between the four strains of catfish. Cathepsin L activity was highest in March, and cathepsin D activity was highest in March and May. Cathepsin B activity was generally lower than the activities of either cathepsin L or D, with the highest levels occurring in November, December, and March. This is the first report of cathepsin activities and their relationships to other reproductive parameters in channel catfish.

Investigation of de novo cholesterol synthetic capacity in the gonads of goldfish (Carassius auratus) exposed to the phytosterol beta-sitosterol

Total and intra-mitochondrial gonadal cholesterol concentrations are decreased in fish exposed to the phytoestrogen beta-sitosterol (beta-sit). The present study examined the potential for beta-sit to disrupt de novo cholesterol synthesis in the gonads of goldfish exposed to 200 microgram/g beta-sit and 10 microgram/g 17beta-estradiol (E2; estrogenic control) by intra-peritoneal Silastic® implants for 21 days. The de novo cholesterol synthetic capacity was estimated by incubating gonadal tissue with 14C-acetate for a period of 18 hours, followed by chloroform/methanol lipid extraction and thin layer chromatography (TLC) lipid separation. Lipid classes were confirmed using infrared spectroscopy. Plasma testosterone (T) and total cholesterol concentration were measured and gonadosomatic index (GSI) was calculated. Plasma T was significantly reduced in male beta-sit-treated fish compared to control and E2-treated fish (p < 0.001). 14C-Acetate incorporation into cholesterol and cholesterol esters was not significantly different among treatment groups for male and female fish, however, 14C-enrichment was higher than expected in both triglycerides (TG) and free fatty acids (FFA). FFA incorporation was significantly higher in male control fish than either beta-sit or E2 treatments (p = 0.005). Plasma cholesterol concentration was significantly increased in the male beta-sit treatment group compared to controls (p = 0.027). These results indicate gonadal de novo cholesterol biosynthetic capacity is not disrupted by beta-sit or E2 treatment in early recrudescing male or female goldfish, while plasma cholesterol and steroid concentrations are sensitive to beta-sit exposure.

Use of ethanol for preserving steroid and indoleamine hormones in bird plasma

Endocrinological research on wild animals inhabiting remote areas has been hampered by the need to store plasma samples at subzero temperatures. In an attempt to remedy this logistical issue, we here investigate the use of ethanol as an alternative to freezing for the preservation of steroid and indoleamine hormones in avian plasma. Known quantities of the steroids 5α-dihydrotestosterone (DHT), testosterone, 17β-estradiol, corticosterone, and the indoleamine melatonin were added to a stripped pool of chicken plasma. Samples were either immediately frozen at −40 °C, or treated with pure ethanol. Ethanol-treated samples were either immediately frozen, or—to simulate storage conditions at various field locations—left sitting at room temperature for one to two months, or incubated at 36 °C for one month before all treatment groups were frozen at −40 °C. All samples were then analyzed by radioimmunoassay. For DHT and estradiol there were no differences among treatment groups suggesting that ethanol-treatment is as effective as immediate freezing in preserving plasma steroid concentrations. For testosterone, corticosterone and melatonin ethanol-treated samples differed significantly from immediately frozen samples suggesting that caution is needed when comparing absolute concentrations of hormones between samples preserved in different ways. However, differences among ethanol-treated samples in general were small, demonstrating the feasibility of this preservation method in the field at remote locations.

Anticipation and consumption of food each increase the concentration of neuroactive steroids in rat brain and plasma

Stressful stimuli and anxiogenic drugs increase the plasma and brain concentrations of neuroactive steroids. Moreover, in rats trained to consume their daily meal during a fixed period, the anticipation of food is associated with changes in the function of various neurotransmitter systems. We have now evaluated the effects of anticipation and consumption of food in such trained rats on the plasma and brain concentrations of 3α-hydroxy-5α-pregnan-20-one (3α,5α-TH PROG) and 3α,21-dihydroxy-5α-pregnan-20-one (3α,5α-TH DOC), two potent endogenous positive modulators of type A receptors for γ-aminobutyric acid (GABA). The abundance of these neuroactive steroids was increased in both the cerebral cortex and plasma of the rats during both food anticipation and consumption. In contrast, the concentration of their precursor, progesterone, was increased in the brain only during food consumption, whereas it was increased in plasma only during food anticipation. Intraperitoneal administration of the selective agonist abecarnil (0.1 mg/kg) 40 min before food presentation prevented the increase in the brain levels of 3α,5α-TH PROG and 3α,5α-TH DOC during food anticipation but not that associated with consumption. The change in emotional state associated with food anticipation may thus result in an increase in the plasma and brain levels of 3α,5α-TH PROG and 3α,5α-TH DOC in a manner sensitive to the activation of GABA A receptor-mediated neurotransmission. A different mechanism, insensitive to activation of such transmission, may underlie the changes in the concentrations of these neuroactive steroids during food consumption.

Development and Performance Evaluation of a Tandem Mass Spectrometry Assay for 4 Adrenal Steroids

Congenital adrenal hyperplasia is a group of autosomal recessive disorders caused by a deficiency of 1 of 4 enzymes required for the synthesis of glucocorticoids, mineralocorticoids, and sex hormones. Analysis of 11-deoxycortisol (11DC), 17-hydroxyprogesterone (17OHP), 17-hydroxypregnenolone (17OHPr), and pregnenolone (Pr) in blood allows detection of these enzyme defects. The steroids were extracted from 200 microL of serum or plasma by solid-phase extraction, derivatized to form oximes, and extracted again with methyl t-butyl ether. Instrumental analysis was performed on an API 4000 tandem mass spectrometer with electrospray ionization in positive mode and multiple reaction-monitoring acquisition. The limits of detection were 0.025 microg/L for 11DC, 17OHP, and Pr and 0.10 microg/L for 17OHPr. The method was linear to 100 microg/L for 11DC, 17OHP, and Pr, respectively, and to 40 microg/L for 17OHPr. Within- and between-run (total) imprecision (CVs) were <7.1% and 11%, respectively. Reference intervals for children in Tanner stages 1 through 5 and adult males and females for 17OHP, 11DC, Pr, and 17OHPr were established. Prepared samples were stable for >72 h. The detection limit and selectivity of this method and its small sample volume requirement allow analysis of endogenous concentrations of adrenal steroids in serum or plasma from children and adults. The method thus has an important potential role in the evaluation of the status of 4 of the enzymes involved in adrenal steroid biosynthesis.

Hormonal correlates of parental behavior in yellow-eyed penguins (Megadyptes antipodes)

Penguins show varying degrees of brood reduction behavior, from obligate brood reducers to brood maximizers, and we hypothesize that this is associated with differences in prolactin secretion. To address this hypothesis, we determined the breeding season prolactin profile of the yellow-eyed penguin (Megadyptes antipodes) for comparison with those of other penguin species found in the literature. We also measured sex steroid plasma concentrations to better characterize the reproductive cycle of the species. Plasma concentrations of prolactin increased from early in the season, reaching a peak during late incubation, and remained elevated up to the guard period. This general pattern was similar to that of other penguins for which we have corresponding data. However, we found that throughout the laying period, prolactin titers in yellow-eyed penguins remained elevated while they fell to basal levels after the laying of the first egg in macaroni penguins, which corresponds to differences in incubation behavior during this time. We conclude, therefore, that differences in the brood reduction behavior in penguins, may be reflected in the pattern of PRL concentrations around the time of egg laying.

Yolk androgens vary inversely to maternal androgens in Eastern Bluebirds: an experimental study

1 Female birds deposit variable amounts of androgens in the yolks of their eggs, and it has been suggested that yolk androgen deposition is an adaptive mechanism preparing offspring for a competitive environment. Breeding pairs of Eastern Bluebirds (Sialia sialis) Linnaeus were stimulated with an intruder presentation while ovarian follicles were developing. Yolk steroid concentrations in eggs laid by stimulated females were then compared with yolk steroid concentrations in eggs laid by control females. Additionally, blood samples taken from a subset of control and stimulated females were analysed for plasma steroid hormone concentrations. We predicted that female bluebirds experiencing a simulated intrusion would experience increased levels of circulating plasma androgens that would be reflected by larger amounts of androgens deposited in their eggs compared with control females. 2 Patterns of steroid concentrations differed between egg yolks and female plasma. In egg yolks, androstenedione was the predominant hormone, followed by testosterone. Yolks contained minimal amounts of both corticosterone and oestradiol. In female plasma, however, corticosterone was the predominant hormone, while sex steroids were found at low levels. 3 Yolk steroid concentrations did not vary with laying order in either the control or the stimulated group, a result expected due to the relatively synchronous nature of incubation behaviour exhibited by Eastern Bluebird females. 4 Yolk androgen concentrations in eggs laid by stimulated females were significantly higher than in those laid by control females, suggesting that females increase yolk androgen deposition in response to aggressive encounters. 5 Females exposed to an intruder presentation contained significantly lower levels of plasma androgens than control females. We suggest that the deposition of androgens in the eggs serves as an adaptive method of regulating circulating androgen levels in the female, preventing potentially disruptive elevations in circulating androgen concentrations during a particularly sensitive period in the reproductive cycle.

Up-regulation of the alligator CYP3A77 gene by toxaphene and dexamethasone and its short term effect on plasma testosterone concentrations

In this study we describe an alligator hepatic CYP3A gene, CYP3A77, which is inducible by dexamethasone and toxaphene. CYP3A plays a broad role in biotransforming both exogenous compounds and endogenous hormones such as testosterone and estradiol. Alligators collected from sites in Florida that are contaminated with organochlorine compounds exhibit differences in sex steroid concentrations. Many organochlorine compounds induce CYP3A expression in other vertebrates; hence, CYP3A induction by organochlorine contaminants could increase biotransformation and clearance of sex steroids by CYP3A and provide a plausible mechanism for the lowering of endogenous sex steroid concentrations in alligator plasma. We used real time PCR to examine whether known and suspected CYP3A inducers (dexamethasone, metyrapone, rifampicin, and toxaphene) up-regulate steady state levels of hepatic CYP3A77 transcript to determine if induction patterns in female juvenile alligators are similar to those reported in other vertebrates and whether toxaphene, an organochlorine compound found in high concentrations in Lake Apopka alligators, induces this gene. Estrogen receptor α (ERα), estrogen receptor β (ERβ), androgen receptor (AR), glucocorticoid receptor (GR), progesterone receptor (PR), and steroid-xenobiotic receptor (SXR) transcripts were also measured to determine whether any of these nuclear receptors are also regulated by these compounds in alligators. Dexamethasone (4.2-fold) and toxaphene (3.5-fold) significantly induced CYP3A77 gene transcript, whereas rifampicin (2.8-fold) and metyrapone (2.1-fold) up-regulated ERβ after 24 h. None of the compounds significantly up-regulated AR, ERα, GR, PR, or SXR over this time period. Plasma testosterone (T) did not change significantly after 24 h in alligators from any of the treatment groups. Dexamethasone treated animals exhibited a strong relationship between the 24 h plasma T concentrations and CYP3A77 ( R 2 = 0.9, positive) and SXR ( R 2 = 0.77, negative) transcripts, which suggests that the expression of these genes is related to plasma T in alligators. In light of our findings, we hypothesized that higher steady state CYP3A77 (and possibly SXR) gene expression would be observed in alligators collected from Lake Apopka, a polluted lake containing organochlorine compounds known to induce CYP3A isoforms in other taxa. Therefore, we measured basal levels of CYP3A77 and SXR gene transcripts in wild juvenile alligators collected from Orange Lake (reference lake), Lake Woodruff (reference lake), and Lake Apopka (contaminated lake). We found that no differences existed in CYP3A77 or SXR gene expression among animals from the lakes sampled suggesting that exposure to organochlorine compounds at concentrations present in Lake Apopka does not lead to variation in the expression of these genes, although capture stress could be interfering with these results since the glucocorticoid dexamethasone induces CYP3A77 transcript in alligators.

Effects of the Feedlot Contaminant 17α-Trenbolone on Reproductive Endocrinology of the Fathead Minnow

Trenbolone acetate is a growth promoter widely used for beef production in the U.S. Two biologically active metabolites of the acetate, 17beta- and 17alpha-trenbolone, are ligands of vertebrate androgen receptors and comparatively stable in the waste of treated animals. Both have been detected in surface water associated with beef feedlots, suggesting a potential risk to aquatic animals. In previous work we evaluated the effects of beta-trenbolone on reproductive endocrinology of the fathead minnow (Pimephales promelas) in a 21-day test. The purpose of the present study was to conduct a similar set of experiments with alpha-trenbolone which, based on binding to mammalian androgen receptors, was expected to be less potent than beta-trenbolone. Fecundity of the fish was significantly reduced by alpha-trenbolone with an EC50 (95% confidence interval) of 0.011 (0.007-0.016) microg/L. In females, alpha-trenbolone reduced plasma vitellogenin and steroid concentrations and also induced the production of dorsal nuptial tubercles, structures normally present only in spawning males. Overall, effects of alpha-trenbolone on the reproductive system of the fish were qualitatively and quantitatively quite similar to those caused by beta-trenbolone. Part of this similarity might arise from the fact that a substantial amount of the alpha-trenbolone appeared to be converted to beta-trenbolone by the fish. Tissue concentrations of the beta-isomer were consistently similar to or greater than concentrations of alpha-trenbolone, despite the fact that no beta-trenbolone was detected in the exposure water. The present study demonstrates the importance of considering both alpha- and beta-trenbolone in assessing the potential ecological risk of androgens associated with beef feedlot discharges.

Steroid biosynthetic enzyme activities in leachate-exposed female perch ( Perca fluviatilis) as biomarkers for endocrine disruption

Studies have shown that adult female perch in a freshwater lake, Molnbyggen, Sweden, have a reproductive disorder caused by unidentified endocrine disrupting compounds (EDCs) leaching from a local refuse dump. The adverse effects include shallow open sores, low ratio of sexually mature individuals, low gonadosomatic index and low circulating levels of androgens. We hypothesised that the low androgen levels could be a result of impaired production and/or stimulated excretion of androgens by EDCs. From October 2000 to November 2001, at time-points important in the perch reproductive cycle, adult female perch were collected in Molnbyggen and in the reference lake, Djursjön. The activities of three key enzymes in androgen biosynthesis: 17α-hydroxylase (17OHlase), 17,20-lyase (lyase) and 17β-hydroxysteroid dehydrogenase (17βHSD) were determined in head kidney or ovary. The relationship between enzyme activities and plasma steroid concentrations was examined. Ovarian histopathology and the determination of brain aromatase activity were also included in the study. Similar 17OHlase, 17βHSD and aromatase activities were found in Molnbyggen females and reference fish throughout the year. Head kidney 17OHlase showed a positive correlation to cortisol levels ( r = 0.754; p < 0.001) but not to androgen levels. Molnbyggen females exhibited lower ovarian lyase activity during vitellogenesis than reference fish. Atretic oocytes were on most occasions more frequent in sexually immature than in sexually mature females. The results suggest that neither 17OHlase, 17βHSD nor aromatase is the target for EDCs disrupting the androgen homeostasis of exposed female perch. Further investigation is needed to establish the role of decreased ovarian lyase activity in endocrine homeostasis, but the possibility of increased excretion of androgens should also be examined.

Plasma steroid hormone concentrations, aromatase activities and GSI in ranid frogs collected from agricultural and non-agricultural sites in Michigan (USA)

The triazine herbicide atrazine has been hypothesized to disrupt sexual development in frogs by up-regulating aromatase activity, resulting in greater estradiol (E2) concentrations and causing feminization in males. The goal of this study was to collect native ranid frogs from atrazine-exposed ponds and determine whether relationships exist between measured atrazine concentrations and the gonadosomatic index (GSI), plasma concentrations of testosterone (T), E2 or 11-ketotestosterone (KT), or with aromatase activity. In the summer of 2002 and 2003, adult and juvenile green frogs ( Rana clamitans), bullfrogs ( R. catesbeiana) and Northern leopard frogs ( R. pipiens) were collected from areas with extensive corn cultivation and areas where there was little agricultural activity in south-central Michigan. Atrazine concentrations were below the limit of quantification at non-agricultural sites. Atrazine concentrations did not exceed 2 μg/L at most agricultural sites, but a concentration of 250 μg atrazine/L was measured in one sample from one site in 2002. Plasma steroid concentrations varied among locations. Aromatase activity was measurable in less than 11% of testes in adult males, and in less than 4% of testes in juvenile males. Median aromatase activities in ovaries of adult females ranged from 3 to 245 pmol/h/mg protein, and maximum activities were 2.5-fold greater in juveniles than in adults. Atrazine concentrations were not significantly correlated with any of the parameters measured in this study. These results indicate that atrazine does not up-regulate aromatase in green frogs in the wild, and does not appear to affect plasma steroid hormone concentrations.

Endocrine Disruption Induced by Organochlorines (OCs): Field Studies And Experimental Models

Long-range transport of persistent organic compounds by air and ocean currents from industrialized areas resulted in high levels of these pollutants in food webs in the Svalbard area. With the aim to test if organochlorine (OC) exposure in free-living polar bears from Svalbard affected their plasma steroid hormone concentrations, it was found that polychlorinated biphenyls (PCBs) were associated with increased progesterone levels in females. The sum of pesticides (∑pesticides) and ∑PCBs contributed significantly negative to the variation of the plasma testosterone in males, and the overall contribution of the OCs to the plasma cortisol variation was negative. A second objective was to study the effects of selected OCs (i.e., PCB 153 and PCB 126) on animal health as a consequence of effects on endocrine-regulated functions such as reproduction and immunity in a goat model focusing on long-term and low-level exposure during the periods of fetal development and in the neonatal period. Additionally, acute exposure was studied in adult mice. The results indicated that exposure to low doses of PCB 153 in utero and in the suckling period influenced reproductive functions and both PCB 153 and PCB 126 exerted immunomodulatory effects on the offspring, whereas acute exposure of adult mice had minor effects on male reproductive function.

Subjective effects and changes in steroid hormone concentrations in humans following acute consumption of alcohol

GABAA receptors are an important site of action of endogenous neurosteroids and an important mediator of several behavioral effects of alcohol. This study examined the effects of alcohol on plasma steroid hormone concentrations on the hypothesis that the endocrine effects mediate some of the subjective effects of alcohol. Thirty-two healthy subjects (17 men) with no history of a substance use disorder participated in this human laboratory study. All subjects consumed three standard drinks of grain alcohol. Subjective measures and blood samples for steroid concentrations were collected at baseline and 40 min after alcohol consumption. Alcohol increased self-reported stimulation, alcohol liking, and desire for more alcohol. Alcohol also increased pregnenolone (PREG) and dehydroepiandrosterone (DHEA) concentrations, while it decreased progesterone (PROG) and allopregnanolone (ALLO) concentrations, as well as ALLO/PREG and PROG/PREG ratios. In men, the change in PREG concentration was significantly correlated with alcohol liking, while the alcohol-induced change in ALLO concentration correlated significantly with both alcohol liking and desire for more alcohol. These findings provide preliminary support for the hypothesis that endogenous neurosteroids mediate some of the subjective effects of alcohol. Efforts to replicate these findings should aim to specify more clearly the nature and time course of the effects.

Relations between Plasma IGF-I Concentrations during Treatment with CIDR-based or Ovsynch Protocol for Timed AI and Conception in Early Postpartum Japanese Black Beef Cows

We examined the relations between plasma insulin-like growth factor (IGF) -I concentrations during treatment with CIDR-based or Ovsynch protocol for timed AI and conception and plasma steroid concentrations in early postpartum Japanese Black beef cows. Cows in the control group (Ovsynch; n = 21) underwent Ovsynch protocol (GnRH analogue on Day 0, PGF(2alpha) analogue on Day 7, and GnRH analogue on Day 9), with AI on Day 10, approximately 20 h after the second GnRH treatment. Cows in the Ovsynch+CIDR group (n = 22) received Ovsynch protocol plus a CIDR for 7 days (starting on Day 0). Cows in the further treatment group (EB+CIDR+GnRH; n = 22) received 2 mg of estradiol benzoate (EB) on Day 0 in lieu of the first GnRH treatment, followed by the same treatment as in the Ovsynch+CIDR protocol. Plasma IGF-I concentrations were determined on Days -7, 0, 7, 9 and 17. Conception rates were improved in the CIDR-combined groups (both CIDR-treated groups were combined) relative to Ovsynch group (P < 0.05) for cows with low IGF-I concentrations (<1,000 ng/ml) on Days -7, 0, and 7, but improved conception rate produced by the CIDR-based protocols did not occur in cows with a high IGF-I concentration (> or =1,000 ng/ml). Plasma estradiol-17beta concentrations increased from Day 0 to 7 (P < 0.05) and were unchanged from Day 7 to 9 in the Ovsynch group with low IGF-I concentrations on Day 0, while they were unchanged from Day 0 to 7 and increased from Day 7 to 9 (P < 0.05) in the Ovsynch group with high IGF-I concentrations on Day 0 and in the CIDR-combined group. Plasma progesterone concentrations in the Ovsynch group with low IGF-I concentrations on Day 0 were higher on Day 14 than in the Ovsynch group with high IGF-I concentrations on Day 0 and in the CIDR-combined group (P < 0.05). In conclusion, CIDR-based protocols may improve conception relative to Ovsynch in early postpartum beef cows with lower plasma IGF-I concentrations at the start of the protocols. This improvement is probably due to prevention of premature increases of estradiol-17beta and progesterone concentrations, which occurred in cows with low IGF-I concentrations treated with Ovsynch, by the CIDR treatment.

Effect ofGinkgo bilobaExtract on Plasma Steroid Concentrations in Healthy Volunteers: A Pilot Study

To determine if a standardized ginkgo supplement significantly alters concentrations of circulating androgenic steroids in humans. Open-label, fixed-treatment order, crossover study. University general clinical research center. Eleven healthy volunteers (six men, five women). Volunteers received ginkgo biloba 240 mg/day for 14 days. Plasma concentrations of cortisol, 11-deoxycortisol, 17alpha-hydroxyprogesterone, testosterone, dihydrotestosterone, dehydroepiandrosterone sulfate, sex hormone-binding globulin, androstenedione, and free testosterone, as well as free androgen index and combined concentrations of androsterone sulfate and epiandrosterone sulfate, were analyzed in all subjects before and after their 14-day course of ginkgo biloba. Ginkgo biloba did not significantly alter endogenous steroid levels compared with baseline values (p < 0.05). A 14-day oral administration of a widely used, standardized ginkgo extract at a generally advocated dosage of 240 mg/day did not significantly alter concentrations of major circulating steroids in men and women.

Ketogenic diet decreases circulating concentrations of neuroactive steroids of female rats

Ketogenic diet (KD) is used to manage intractable epilepsy; however, the mechanisms underlying its therapeutic effects are not known. Steroid hormones, such as progesterone and testosterone, are derived from cholesterol, and are readily 5α-reduced to dihydroprogesterone and dihydrotestosterone, which are subsequently converted to 5α-pregnan-3α-ol-20-one (3α,5α-THP) and 3α-androstanediol, neuroactive steroids that can influence seizures. The present study examined the effects of the KD on circulating concentrations of these neuroactive steroids, and their precursors, in intact female rats. Thirty-six, 22-day-old female Sprague–Dawley rats (weaned at 21 days) were fasted for 8hours prior to placement on one of three dietary regimens for 6 weeks: ad libitum chow, calorie-restricted chow, or KD. After 6 weeks of the diet, when six rats in each dietary condition were in diestrus and six were in behavioral estrus, all rats were administered pentylenetetrazole (PTZ, 70mg/kg, IP). The latency and incidence of seizures were recorded by an observer who was uninformed of the estrous cycle and dietary treatment conditions of the rats. Immediately after each test, trunk blood was obtained for later measurement of pregnane (progesterone, dihydroprogesterone, 3α,5α-THP) and androstane (testosterone, dihydrotestosterone, 3α-androstanediol) neuroactive steroid concentrations in plasma by radioimmunoassay. KD tended to lengthen the latency to, and significantly reduced the number of, PTZ-induced barrel roll seizures. KD also significantly reduced plasma levels of the pregnane (dihydroprogesterone, 3α,5α-THP) and androstane (dihydrotestosterone, 3α-androstanediol) 5α-reduced metabolites. These data suggest that levels of pregnane and androstane neuroactive steroids, or their precursors, may underlie some of the antiseizure effects of KD.