Effects of testosterone and β‐glucan on immune functions in tench

A hormone manipulation was performed to examine the effects of testosterone on basal and β‐glucan‐induced immune functions in wild‐caught male and female tench Tinca tinca . Testosterone administration elevated testosterone concentration in plasma, but did not suppress lytic activity of plasma or the chemiluminescence response of blood or head kidney phagocytes in any of the three successive samples or in any of the treatment groups. Both testosterone and β‐glucan administrations had a negative effect on the relative mass of the spleen, and testosterone‐treated fish lost more mass than control fish. Males had a relatively larger spleen than females, but there were no gender differences in immune function. β‐glucan‐administration did not affect the plasma testosterone concentration.     

Reproductive biology of female big‐bellied seahorses

In this study, ovarian morphology, reproductive condition and sex steroid levels were investigated in the big‐bellied seahorse Hippocampus abdominalis , collected by snorkel and SCUBA diving in Wellington Harbour, New Zealand. Within the ovary, oocytes were contained between an outer muscular wall and an inner layer of luminal epithelium. Two germinal ridges ran along the entire length of the ovary. In cross‐section, oocytes were arranged in sequential order of development beginning at the germinal ridges and ending at the mature edge. Ovarian lamellae were absent. Vitellogenic and advanced cortical alveoli oocytes were elongated in shape, whereas maturing oocytes were distinctively pear‐shaped. Mature oocytes were large (2·6 – 4·4 mm in length) and aligned with the animal pole towards the muscular wall. Reproductively mature females were found throughout the year indicating a protracted reproductive season. The gonado‐somatic index was significantly different between all ovarian stages, but the hepato‐somatic index was not. Females with previtellogenic ovaries had significantly higher plasma concentrations of testosterone than females with vitellogenic or maturing ovaries. There was no significant difference in plasma concentrations of testosterone between females with vitellogenic or maturing ovaries, or in plasma concentrations of 17β‐oestradiol between females in all ovarian stages. This study contributes to the knowledge on the reproductive biology of female syngnathids.     

Evaluation of biochemical methods for the non‐destructive identification of sex in upstream migrating salmon and sea trout

Female‐specific markers of reproductive activity [plasma 17β‐oestradiol (E2), vitellogenin (VTG) and alkali‐labile phosphoprotein phosphorous (ALP)] were measured over 12 months in a captive population of brown trout Salmo trutta . During the early months of the reproductive season (February to May) and using the concentration of plasma E2 or plasma ALP as a marker for females the proportion of fish in which sex was misidentified was high (15–50%). The misidentification rate was considerably lower (1–8%) using plasma VTG. Preliminary evaluation of a commercial immunochromatographic VTG test system as a screen for the presence or absence of VTG in plasma from brown trout provided results that were consistent with those obtained from direct measurement of plasma VTG levels by enzyme‐linked immunosorbent assay (ELISA). These preliminary conclusions were verified by sampling upstream‐migrating anadromous brown trout, sea trout, and Atlantic salmon Salmo salar trapped over a 6 month period. Plasma E2 levels did not satisfactorily discriminate between male and female sea trout and Atlantic salmon. Plasma VTG levels in both species, however, were bimodally distributed and it was assumed that this divergence corresponded to male (plasma VTG levels <10 μg ml⁻¹) and female (plasma VTG levels >800 μg ml⁻¹) fishes. Plasma ALP provided a more accurate indication of sex in the wild Atlantic salmon and sea trout than was suggested by the pilot study on captive brown trout. The commercial immunochromatographic VTG test system provided results that were wholly consistent with the data obtained from the trapped fishes by direct measurement of plasma VTG.     

Sex steroid binding proteins in the plasma of hatchling <Emphasis Type="Italic">Chelonia mydas</Emphasis>

Sex steroid binding proteins were identified in hatchling female and male Chelonia mydas by dialysis and steady-state gel electrophoresis when examined at 4 degrees C. A testosterone binding protein with high binding affinity (K (a) = 0.98 +/- 0.5 x 10(8) M(-1)) and low to moderate binding capacity (B (max) = 7.58 +/- 4.2 x 10(-5) M) was observed in male hatchlings. An oestradiol binding protein with high affinity (K (a) = 0.35 +/- 1.8 x 10(8) M(-1)) and low to moderate binding capacity (B (max) = 0.16 +/- 0.5 x 10(-4) M) was identified in female hatchlings. This study confirmed that sex steroid binding proteins (SSBPs) become inactivate in both sexes at 36 degrees C, the maximum body temperature of sea turtle hatchlings at emergence. The inactivation of SSBPs at this temperature indicates that sex steroid hormones circulate freely in the body of the green turtles and are biologically available in the blood plasma. This observation is consistent with female and male hatchling C. mydas having different physiological (hormonal) and developmental requirements around the time of emergence. Moreover, concurrently conducted competition studies showed that sex steroids including testosterone and oestradiol do compete for binding sites in both male and female C. mydas hatchling plasma. Competition also occurred between testosterone and dihydrotestosterone for binding sites in the male C. mydas plasma. However, competition studies in the plasma of female hatchling C. mydas demonstrate that oestrone does not compete with oestradiol for binding sites.     

Social interactions unmask sex differences in humoral immunity in voles

Sex differences in immune function are well established among laboratory rodents, with males typically having lower immunity than females. This sex difference may reflect the suppressive effects of testosterone on immune function. Because polygynous males generally have higher circulating testosterone concentrations than monogamous males, sex differences in immune function are hypothesized to be more pronounced among polygynous as compared to monogamous species. Sex differences in immune function have not been consistently observed among individually housed Microtus in the laboratory; thus, social interactions are hypothesized to be necessary for the expression of sex differences in immune function. We assessed the effect of differential housing conditions on humoral immunity and steroid hormone concentrations in polygynous meadow voles Microtus pennsylvanicus, and monogamous prairie voles M. ochrogaster. We examined humoral immunity by immunizing voles with keyhole limpet haemocyanin (KLH) and measuring antibody production 5, 10, 15 and 30 days postimmunization. Overall, meadow voles mounted higher anti-KLH immunoglobulin (Ig)M and IgG responses than prairie voles, regardless of the housing condition. Sex differences in antibody production were only observed among meadow voles housed in pairs, in which females had higher anti-KLH IgM and IgG responses than males. Sex differences in antibody production were not observed among prairie voles or meadow voles housed individually. Sex and species differences in circulating oestradiol, testosterone, and corticosterone concentrations were not related to differences in humoral immunity. These data suggest that sex differences in immune function are more pronounced among polygynous species than monogamous species, but may be context dependent. Copyright 1999 The Association for the Study of Animal Behaviour.     

Patterns of oocyte growth, vitellogenin and gonadal steroid concentrations in greenback flounder

The pattern of oocyte development in association with changes of plasma concentrations of vitellogenin (Vtg), 17β‐oestradiol (E₂) and testosterone (T) was investigated in maturing female greenback flounder Rhombosolea tapirina over the first part of a reproductive season (February to June). Examination of oocyte size‐frequency distributions showed that the oocyte developmental pattern in R. tapirina is multiple group synchrony, and that reproductively mature fish were present at all sampling times. There were no significant temporal variations in the gonado‐somatic index ( I _G), hepato‐somatic index ( I _H), or plasma concentrations of Vtg, E₂ and T during the sampling period, which indicates that reproductive development is not synchronized within the population. Significant increases in I _G, I _H and plasma concentrations of Vtg, E₂ and T, however, were observed in vitellogenic fish, and in fish undergoing final maturation. A positive relationship was also found between the growth of oocytes and plasma concentrations of Vtg, E₂ and T, although the patterns of increase were different for each variable. Plasma concentrations of Vtg and E₂ rose steadily across oocyte sizes from 100 to 450 μm, but the rate of increase of plasma E₂ was slower than that of Vtg, and both reached a saturated concentration at oocyte sizes of c . 450 μm. In contrast, plasma concentrations of T showed no marked increase until oocytes grew beyond 400 μm.     

Biological effect of vaccination can be assessed directly from diluted whole blood of rainbow trout using homologous blood phagocytes as immunosensors

A rapid and simple method is presented for determining antibody activity following vaccination, directly from diluted fish blood. The proposed method evaluates the effects of specific antibodies on ingestion by blood phagocytes, and may be used for measuring antibody levels following vaccination. The enhancing effect of trout IgM on ingestion was measured by luminol-amplified chemiluminescence (CL) emission of blood phagocytes. Respiratory burst (RB) activity of blood phagocytes was induced with the strain MT004 of bacterial fish pathogen Aeromonas salmonicida. To determine the boosting level of specific IgM on ingestion, various volumes of purified trout IgM containing specific antibodies against A. salmonicida were added to blood samples collected from non-vaccinated fish, and the RB activity of blood phagocytes was measured. The presence of antibodies in plasma of artificially prepared immune blood (AIB) was confirmed using enzyme-linked immunosorbent assay (ELISA). At a final blood dilution of 1:250, the mean RB activity of blood samples boosted with IgM was more than seven times higher, compared to other tested blood dilutions boosted with equal amount of IgM. Accordingly, a dilution of 1:250 was employed in the field study of vaccinated and non-vaccinated fish. The levels of A. salmonicida-specific antibodies in plasma samples of vaccinated and non-vaccinated fish were additionally confirmed with the ELISA assay. Based on these results, it is proposed that the biological activity of elicited antibodies can be assessed directly from diluted fish blood, using homologous blood neutrophils as immune sensors.     

Serum levels of testosterone, 11‐ketotestosterone and oestradiol‐17β in three species of sturgeon during gonadal development and final maturation induced by hormonal treatment

Changes in serum concentrations of two androgens, testosterone (T) and 11‐ketotestosterone (11KT), and oestradiol‐17β(E2) in male and female giant sturgeon Huso huso , Russian sturgeon Acipenser gueldenstaedtii and stellate sturgeon Acipenser stellatus were studied at different stages of gonadal maturity and after final maturation induced by hormonal treatment. Both male and female fish displayed a distinct increase in serum steroid concentrations during gonadal development. 11KT levels were significantly higher in males than females, with a positive correlation detected between 11KT and T concentrations. In maturing males and females, higher values of both 11KT and T were observed in stellate sturgeon compared to giant and Russian sturgeons. Vitellogenesis and high E2 levels were correlated in maturing sturgeon females.     

The relationship between body mass index, semen and sex hormones in adult male

This study was aimed at evaluating the relationship between body mass index, sex hormones and semen characteristics in male adults. 120 male adults aged 20 to 50 years who consented to participate in the study were used. Serum samples collected from each subject were analyzed for Luteinizing hormone (LH), Follicle stimulating hormone (FSH), Prolactin (PRL), Progesterone, Estradiol and testosterone by classical ELISA method. Semen samples obtained by masturbation after 72 hours of abstinence were analyzed for sperm count and motility. The results showed statistically significant correlations at 99% confidence level between body mass index and serum concentrations of progesterone and oestradiol and sperm count. No significant correlations were observed between body mass index and sperm motility, serum concentrations of prolactin, testosterone and luteinizing hormone. In conclusion, this study has shown that statistically significant correlations exist between body mass index, semen characteristics and male sex hormones and may broaden our understanding of the physiology of male fertility/infertility. Keywords: Body mass index, Semen quality, Male sex hormones, Fertility/infertility.     

Follicular fluid steroid levels and subsequent sex of bovine embryos

On the basis of evidence suggesting a maternal involvement in the determination of the sex of the offspring, we took ova at the point of ovulation from crossbred heifers, fertilised them, and established the sex of the embryos. At the same time we took individual-matched samples of follicular fluid from each follicle of origin, and measured the levels of testosterone and oestradiol, blind to the sex of the embryo. We found no effect of oestradiol on sex in either primary or subordinate follicles. But bovine ova from subordinate follicles that had follicular fluid with a high concentration of testosterone (in vivo) were later more likely to be fertilised by a Y-chromosome-bearing spermatozoon (in vitro). These, along with similar results from other researchers, suggest that further study of the relationship between mammalian follicular hormones at the time of conception and subsequent sex of offspring, may help resolve some of the problems associated with theories of adaptive control of the sex ratio in mammals.     

Testosterone, dihydrotestosterone and oestradiol levels in postmenopausal breast cancer tissues

The ability of breast tumours to synthesize hormones is well recognized, and local production of sex steroids is thought to play a role in breast cancer growth. We measured the intratumour and circulating levels of testosterone, dihydrotestosterone (DHT) and oestradiol in 35 histologically confirmed carcinomatous mammary tissues obtained at breast surgery from 34 postmenopausal patients, age 50–85 years. Intra-tissue steroids were extracted with ethanol:acetone (1:1; v/v), defatted with 70% methanol in water, and extracted with ether. Steroids, from tissue and serum, were separated by partition chromatography on celite columns and were measured by RIA. Intratumour testosterone and DHT concentrations were significantly correlated, after the exclusion of an outlier (r_s = 0.71; P = 0.0001). No association was found between oestradiol and either of the two androgens. Mean oestradiol and DHT concentrations were significantly higher in tissue than in blood (P = 0.0001). Mean testosterone levels in tissues did not significantly differ from those measured in blood. Our data suggest that at least a part of intratissue DHT is produced locally from testosterone. The meaning of high oestradiol and DHT levels in cancer tissue still needs to be defined.     

Comparing plasma and faecal measures of steroid hormones in Adelie penguins Pygoscelis adeliae

Physiological measurements of both stress and sex hormones are often used to estimate the consequences of natural or human-induced change in ecological studies of various animals. Different methods of hormone measurement exist, potentially explaining variation in results across studies; methods should be cross-validated to ensure that they correlate. We directly compared faecal and plasma hormone measurements for the first time in a wild free-living species, the Adelie penguin (Pygoscelis adeliae). Blood and faecal samples were simultaneously collected from individual penguins for comparison and assayed for testosterone and corticosterone (or their metabolites). Sex differences and variability within each measure, and correlation of values across measures were compared. For both hormones, plasma samples showed greater variation than faecal samples. Males had higher mean corticosterone concentrations than females, but the difference was only statistically significant in faecal samples. Plasma testosterone, but not faecal testosterone, was significantly higher in males than females. Correlation between sample types was poor overall, and weaker in females than in males, perhaps because measures from plasma represent hormones that are both free and bound to globulins, whereas measures from faeces represent only the free portion. Faecal samples also represent a cumulative measure of hormones over time, as opposed to a plasma ‘snapshot’ concentration. Our data indicate that faecal sampling appears more suitable for assessing baseline hormone concentrations, whilst plasma sampling may best define immediate responses to environmental events. Consequently, future studies should ensure that they select the most appropriate matrix and method of hormone measurement to answer their research questions.     

Measurement of steroid sex hormones in serum: a comparison of radioimmunoassay and mass spectrometry

Concern has been raised about the adequacy of radioimmunoassays to measure steroid sex hormones in population studies. We compared steroid sex hormone measurements in serum by radioimmunoassay with mass spectrometry. Four male and four female serum pools with known relative concentrations of steroid sex hormones were measured multiple times by both methods. Because measurements are expected to increase linearly with concentration for each sex, we examined whether the linear regressions of hormone measurements on concentration were the same for radioimmunoassay and mass spectrometry. Estradiol, estrone, androstenedione, testosterone, and dehydroepiandrosterone sulfate were measured in female pools; testosterone, dihydrotestosterone, androstenedione, and dehydroepiandrosterone sulfate were measured in male pools. Regression slopes for radioimmunoassay and mass spectrometry measurements were comparable for all hormones except androstenedione, which had a steeper slope when measured by mass spectrometry (P < or = 0.02). Intercepts for radioimmunoassay and mass spectrometry were similar and close to zero for estradiol, androstenedione, dehydroepiandrosterone sulfate, and in male samples, testosterone. For testosterone in female samples, estrone, and dihydrotestosterone, radioimmunoassay and mass spectrometry intercepts differed significantly. Standard deviations of individual measurements by radioimmunoassay and mass spectrometry differed by hormone and serum concentration; neither method consistently measured hormone concentrations with less variability. Our findings suggest that although absolute concentrations may differ for some hormones, radioimmunoassay and mass spectrometry can yield similar estimates of between subject differences in serum concentrations of most steroid sex hormones commonly measured in population studies. Relative power of studies using radioimmunoassay and mass spectrometry will depend on the hormones measured and their serum concentrations.     

Evidence that oestrogen exerts an equivalent negative feedback action on LH secretion in male and female ferrets

Gonadally intact male ferrets in breeding condition, which received an aromatase inhibitor, 1,4,6-androstatriene-3,17-dione (ATD) s.c. in Silastic capsules, had significantly more LH pulses and higher mean LH concentrations in plasma than did control males implanted with empty capsules. Aromatase activity in the hypothalamus + preoptic area and temporal lobe was strongly suppressed by ATD treatment whereas circulating concentrations of testosterone and oestradiol were not affected. These results suggest that oestradiol, formed via neural aromatization of circulating testosterone, contributes to the feedback regulation of LH secretion in breeding male ferrets just as oestradiol of ovarian origin controls LH secretion in females. No sex difference was observed in the rate at which mean plasma LH concentrations rose after the removal from gonadectomized ferrets of s.c. Silastic capsules containing oestradiol. Daily s.c. injections of oestradiol in oil caused an equivalent, dose-dependent inhibition of LH pulse frequency and mean LH concentrations in plasma of male and female ferrets. These findings suggest that the negative feedback control of pulsatile LH secretion by oestrogen is not sexually differentiated in this reflexly ovulating species. The ferret appears to differ from spontaneously ovulating mammalian species in which the female is generally more sensitive than the male to the inhibitory feedback action of oestradiol on LH secretion.     

Sex differences in adrenocortical structure and function. XXVIII. ACTH and corticosterone in intact, gonadectomised and gonadal hormone replaced rats

Plasma ACTH and corticosterone (B) concentration, ACTH content in the anterior pituitary gland and B content in the adrenals were measured in intact, gonadectomised and testosterone or estradiol replaced rats. Plasma ACTH and B levels and adrenal B content were higher in female than male rats. Neither orchiectomy nor testosterone replacement had an effect on plasma ACTH and B concentration. Orchiectomy did not affect adrenal B content and decreased pituitary ACTH while testosterone significantly lowered ACTH and B content in studied glands. On the other hand ovariectomy did not change pituitary ACTH and adrenal B content and notably lowered concentrations of these hormones in the blood. Estradiol replacement resulted in an increase in plasma ACTH and B concentrations, an effect accompanied by a marked drop in pituitary ACTH and an increase in adrenal B. These findings indicate the distinct sex differences in basal plasma ACTH and B concentrations with higher values in female rats, an effect dependent on the stimulatory action of estradiol on pituitary-adrenocortical axis.     

Differences of tributyltin accumulation in the masu salmon Oncorhynchus masou between sea‐run and freshwater‐resident types

In order to examine the accumulation pattern of tributyltin (TBT) in relation to the migratory pattern, TBT concentrations in muscles and strontium (Sr) concentrations in otoliths were determined in both sea‐run and freshwater‐resident masu salmon Oncorhynchus masou . Both TBT and Sr concentrations in sea‐run masu salmon were significantly higher than those of freshwater‐residents.     

Effect of sex and gonadal hormones on rat plasma lipids during the development of an essential fatty acid deficiency

1. Male, female and castrated rats treated with oestradiol (30mug./week) or testosterone (2mg./week) were given an essential fatty acid-deficient diet containing 10% of hydrogenated coconut oil for 9 weeks. The concentrations and fatty acid composition of plasma phospholipids, cholesteryl esters and triglycerides were determined. 2. Between the second and third weeks of the deficiency, concentrations of plasma cholesteryl esters, phospholipids and triglycerides decreased, then remained relatively constant. There were no significant differences between males and females, but oestradiol caused a significant rise in plasma phospholipids and triglycerides as compared with testosterone-treated animals. 3. During the first 2 weeks of the deficiency, linoleic acid in the plasma lipids of all groups decreased to low concentrations and changed very little thereafter. 4. Female rats maintained higher percentages and concentrations of arachidonic acid and stearic acid in plasma phospholipids and arachidonic acid in cholesteryl esters than did males. Males had higher proportions of eicosatrienoic acid and oleic acid. There was no sex difference in the fatty acid composition of plasma triglycerides. 5. Oestradiol-treated rats had concentrations of cholesteryl and phospholipid arachidonate comparable with those of female rats and higher than the testosterone-treated group. Eicosatrienoic acid in the oestradiol-treated rats was high and resembled that of the male rats, apparently because of the higher concentration of plasma phospho lipids in this group. 6. Supplementation of the essential fatty acid-deficient rats with linoleate restored plasma cholesteryl and phospholipid linoleate and arachidonate nearly to normal concentrations in a single day. The increase in arachidonic acid in these fractions was accompanied by a similar quantitative decrease in eicosatrienoic acid. 7. These sex differences appear to be related to the smaller size of the female rat and to a more direct influence of oestradiol on the formation or maintenance of phospholipids rich in arachidonic acid.     

c‐erbB‐2 and p53 expression in breast cancer fine needle aspirates

The aim of this study was to co‐evaluate c‐ erbB ‐2 and p53 protein expression in breast cancer fine needle aspirates (FNA) and to compare this with histological variables and the immunohistochemical phenotype of the tumours. Furthermore, we assessed the relationship of c‐ erbB ‐2 and p53 immunocytochemical expression to tumour prognostic factors. We examined 124 breast cancer FNAs and 79 matched surgical specimens using the avidin–biotin complex (ABC) and the alkaline phosphatase immunocytochemical techniques. C‐ erbB ‐2 immunopositivity was detected in 37.9% of the FNAs, while 31.7% were positive for p53. A statistically significant correlation was observed between p53 negativity and absence of c‐ erbB ‐2 immunostaining in the FNAs ( P =0.0007). Smears from infiltrating ductal carcinomas tended to be more frequently positive for p53 (36.7%) than those from lobular carcinomas (11.7%) ( P =0.054). In matched tumour tissues, c‐ erbB ‐2 was positive in 16.7% and p53 in 19% of cases. The immunocytochemical results for both c‐ erbB ‐2 and p53 were significantly correlated with the immunohistochemical results. There was no correlation between c‐ erbB ‐2 and p53 immunostaining, in both FNAs and tissues, and patients' menopausal status, tumour size, grade and lymph node status.     

Fasting modulates metabolic responses to cortisol, GH and IGF‐I in Arctic charr hepatocytes

Hepatocytes in primary culture from fed and 2 month fasted Arctic charr Salvelinus alpinus were exposed to physiological doses of either cortisol, salmon growth hormone (GH), salmon insulin‐like growth factor‐I (IGF‐I) or a combination of salmon GH and salmon IGF‐I. Fasting significantly lowered medium glucose levels compared to the fed fish, but had no significant effects on hepatocyte glycogen content or on the activities of enzymes involved in the intermediary metabolism. Cortisol treatment had no effect on hepatocyte glycogen content or on the enzyme activities investigated, but resulted in a significant increase in medium glucose concentration in hepatocytes isolated from fasted, but not fed fish. GH and IGF‐I treatments, both singly and in combination, significantly increased the glycogen content of hepatocytes isolated from fed fish, with less pronounced effects on hepatocytes isolated from fasted fish. The combination of GH and IGF‐I significantly increased lactate dehydrogenase activity regardless of the feeding state and significantly reduced the phosphenolpyruvate carboxykinase activity and medium glucose concentration in hepatocytes isolated from fed fish. Further, GH and IGF‐I significantly increased the activities of alanine aminotransferase and aspartate aminotransferase in hepatocytes isolated from fasted fish, but not fed fish. There were no effects of GH, IGF‐I, or their combination, on glucose 6‐phosphate dehydrogenase or 3‐hydroxyacyl‐CoA dehydrogenase activities. The results demonstrated that nutritional status of the animal modulates hepatocyte responsiveness to metabolic hormones, and suggested a role for GH and IGF‐I in hepatic glycogen conservation.     

Effects of oestradiol, testosterone and medroxyprogesterone on subcellular fraction marker enzyme activities from rat liver and brain

The following enzymes have been studied (subcellular fractions are shown between parentheses): NAG and beta-glucuronidase (lysosomes); SDH (mitochondrial); glucose-6-phosphatase (endoplasmic reticulum); 5'-nucleotidase and (Na+, K+)Mg2+ ATPase (plasma membranes). Alterations on their activities were observed after subcutaneous injection of sex hormones, compared with controls. NAG activity from liver was always significantly decreased in lysosomal and microsomal fractions after the hormonal treatment. In the same conditions, NAG from brain was always increased. beta-Glucuronidase behaves like NAG in brain; in liver it was not modified by testosterone and it was slightly increased in lysosomal fraction after oestradiol treatment. SDH activity was not modified in mitochondrial fractions from liver, but this activity was always significantly increased in brain. Glucose-6-phosphatase activity was always significantly decreased in microsomal fractions from liver. It was increased in brain after oestradiol and testosterone injection, but medroxyprogesterone treatment caused a decreased activity. 5'-Nucleotidase and (Na+, K+)Mg2+ ATPase from brain were significantly increased in microsomal fractions by oestradiol and testosterone. Medroxyprogesterone, however, caused an increase in ATPase, but did not affect 5'-nucleotidase. Both activities in liver were decreased by oestradiol and increased by testosterone, but medroxyprogesterone caused (Na+, K+)Mg2+ ATPase to rise and 5'-nucleotidase to fall.