nM In Females Research Articles

Normative values for isometric quadriceps peak torque using fixed dynamometry in healthy young adults

RATIONALE: Assessment of muscle strength is recommended to measure weakness and inform exercise prescription in adults undergoing pulmonary rehabilitation. There is a lack of normative data for lower extremity muscle strength using fixed dynamometry in the clinical setting in young adults. OBJECTIVES: Primary objectives were to determine (i) normative values for isometric quadriceps peak torque (QT) using fixed dynamometry and (ii) the relationship between isometric QT with demographics, body composition, habitual physical activity and one-repetition maximum (1-RM) for knee extension. A secondary objective was to develop a preliminary equation to predict 1-RM knee extension using isometric QT. METHODS This was a cross-sectional study of healthy adults aged 18–39 years. Isometric QT was assessed using fixed dynamometry (MedUp®). A 1-RM test was performed in the same setting. Age, sex and body composition using bioelectiral impedance analysis (Tanita, DC-430U) were collected. Physical activity was assessed by the Rapid Assessment of Physical Activity (RAPA). RESULTS Eighty-two participants were included (44 females, 54%). Isometric QT was 89 (77-132) Nm for females and 158 (133-187) Nm for males (p < 0.0001). There was a strong correlation between isometric QT and 1-RM (r = 0.85, p < 0.0001). The multi-linear regression model to predict 1-RM included sex, isometric QT and BMI (F (3, 78) = 60.819; p < 0.001; R 2 = 0.701). CONCLUSION Normative isometric QT values to quantify lower limb strength impairment and a preliminary equation using isometric QT to predict 1-RM and prescribe resistance quadriceps exercise training may inform pulmonary rehabilitation programs for a younger respiratory population. Validation of the 1-RM equation in clinical populations is needed.

Sex differences in wrist torque and endurance-Biomechanical factors associated with developing lateral epicondylitis of the humerus.

Since eccentric contractions contribute to the development of tendinopathy, sex differences in wrist torque and endurance may be involved in the pathophysiology of lateral epicondylitis and its refractoriness. Therefore, the present study investigated sex differences in wrist torque and endurance. The wrist extension and flexion torques of the 100 wrists of 25 males and 25 females were measured. The following parameters were assessed: muscle strength at the starting- and end point for the measurement, Δ muscle strength, that is, the amount of a loss over time, and the muscle endurance ratio, that is, the decrease rate over time. Each parameter in males and females was statistically analyzed. In wrist extension, muscle strength at the starting point was 6.1 Nm for males and 3.3 Nm for females (p < 0.001); Δ Muscle strength was -0.052 Nm/sfor males and -0.038 Nm/sfor females (p = 0.036); The muscle endurance ratio was 99.1%/sfor males and 98.8%/sfor females (p = 0.015). In wrist flexion, muscle strength at the starting point and absolute value of Δ muscle strength were significantly larger in males than in females; No significant difference was observed in the muscle endurance ratio in wrist flexion between males and females. These results revealed sex differences in wrist torque and endurance. The muscle endurance ratio of the wrist extensors was lower in females than in males, which suggests that females need to exert more effort to maintain the wrist extension position under resistance. This may predispose the wrist extensor muscles in females to eccentric contractions.

Fine Structure of the Compound Eyes of Male and FemaleHeortia vitessoidesMoore (Lepidoptera: Crambidae)

AbstractHeortia vitessoides is a destructive pest of the economically important plant Aquilaria sinensis in China. We investigated the external morphology and ultrastructure of H. vitessoides compound eyes using scanning and transmission electron microscopy. We found that H. vitessoides has superposition eyes, made up of a mean of 3,671 and 3,428 ommatidia in males and females, respectively. The mean ommatidial diameter for males and females was 18.87 and 16.81 µm, respectively. Each ommatidium was capped by a convexly curved corneal facet lens of about 13.85 µm thickness. Corneal nipples measuring 226.36 nm in height in males and 295.48 nm in females, covered the surface of the eyes. Heortia vitessoides eyes are eucone, with each ommatidium having a crystalline cone comprising four cone cells, surrounded by two primary pigment cells. The centrally fused rhabdom of each ommatidium was formed by 8–11 of retinal cells, somewhat more than are typically found in Lepidoptera. The relatively large size of the compound eyes, the large number of ommatidia, large number of retinula cells, and high corneal nipples all suggest that H. vitessoides eyes are adapted to optimize visual sensitivity under dim light conditions.

Trunk musculoskeletal response in maximum voluntary exertions: A combined measurement-modeling investigation

Maximum voluntary exertion (MVE) tasks quantify trunk strength and maximal muscle electromyography (EMG) activities with both clinical and biomechanical implications. The aims here are to evaluate the performance of an existing trunk musculoskeletal model, estimate maximum muscle stresses and spinal forces, and explore likely differences between males and females in maximum voluntary exertions. We, therefore, measured trunk strength and EMG activities of 19 healthy right-handed subjects (9 females and 10 males) in flexion, extension, lateral and axial directions. MVEs for all subjects were then simulated in a subject-specific trunk musculoskeletal model, and estimated muscle activities were compared with EMGs. Analysis of variance was used to compare measured moments and estimated spinal loads at the L5-S1 level between females and males. MVE moments in both sexes were greatest in extension (means of 236 Nm in males and 190 Nm in females) and least in left axial torque (97 Nm in males and 64 Nm in females). Being much greater in lateral and axial MVEs, coupled moments reached ∼50% of primary moments in average. Females exerted less moments in all directions reaching significance except in flexion. Muscle activity estimations were strongly correlated with measurements in flexion and extension (Pearson’s r = 0.69 and 0.76), but the correlations were very weak in lateral and axial MVEs (Pearson’s r = 0.27 and 0.13). Maximum muscle stress was in average 0.80 ± 0.42 MPa but varied among muscles from 0.40 ± 0.22 MPa in rectus abdominis to 0.99 ± 0.29 MPa in external oblique. To estimate maximum muscle stresses and evaluate validity of a musculoskeletal model, MVEs in all directions with all coupled moments should be considered.

Epidemiologic study of tear film lipid layer thickness measurement in the population of Taishitun Community in Beijing

Objective: To investigate the distribution of tear film lipid layer thickness (LLT) and the relationship between symptoms and signs of dry eye and tear film LLT in the population of Taishitun Community in Beijing. Methods: A cross-sectional study. From May 2016 to August 2016, three streets of Taishitun Community were randomly selected as survey districts and 540 persons were taken as investigation subjects. Every participant completed 6 items of dry eye examinations as follows: questionnaire (Ocular Surface Disease Index, OSDI), measurement of tear film LLT, tear film break-up time (TBUT), corneal and conjunctival staining, SchirmerⅠtest and the infrared meibomian photography. According to their age, all participants were divided into four groups: junior group (<18 years old), youth group (18 to 40 years old), middle-aged group (41 to 59 years old) and the elderly group (over 60 years old). With the OSDI criteria, no dry eye symptom group (score, <12 points), mild to moderate dry eye symptom group (score, 12 to 32) and severe dry eye symptom group (score, 33-100) were included. With the statistical methods of variance analysis and multivariate Logistic regression analysis, distribution of the variables of LLT and the relationship between dry eye symptoms and LLT were studied. Results: A total of 473 residents finally participated in this study, and the response ratio was 87.6%. The values of LLT were normally distributed. The average LLT was (59.87±18.50) nm [(60.16±19.15) nm in males and (59.67±18.57) nm in females], and the comparison of LLT with different genders was not statistically significant (t=0.198, P=0.843). The tear film LLT of four different age groups had statistical significance (F=15.092, P<0.05), and increased with age [(56.10±18.33) nm in the junior group, (54.60±16.29) nm in the youth group, (60.61±19.18) nm in the middle-aged group and (73.25±14.58) nm in the elderly group]. The LLT was inversely proportional to the severity of dry eye symptoms. With a thinner LLT, the symptoms of the subjects turned severe. In the elderly with different degrees of symptoms, the LLT was significantly different (F=0.019, P<0.05), while in the youth and middle-aged groups with different degrees of symptoms, the LLT was not significantly different (F=0.096, P>0.05. F=0.538, P>0.05). In the OSDI symptom questionnaire, only blurred vision and decreased visual acuity were related to the tear film LLT (P<0.05). There was no significant correlation between the TBUT, SchirmerⅠtest result, meibomian gland loss rate and the tear film LLT (P>0.05). Conclusions: In Taishitun Community of Beijing, the values of tear film LLT had a normal distribution. The LLT was positively correlated with age, but inversely correlated with the severity of the symptoms of dry eye. There was no significant correlation between the LLT and the TBUT, SchirmerⅠtest result and meibomian gland loss rate.(Chin J Ophthalmol, 2017, 53: 495-501).

Growth hormone, luteinizing hormone, and follicle-stimulating hormone regulation by neuropeptide Y in both sexes of the cichlid fish, Cichlasoma dimerus.

Neuropeptide Y (NPY) is considered the most potent orexigenic peptide, increasing before meal time and during fasting. In teleost, most studies on NPY action upon growth hormone (GH) and luteinizing hormone (LH) were conducted in females or group of animals without sex discrimination. The aim of this study was to evaluate whether NPY modulates the expression and release of GH and gonadotropins in both sexes of Cichlasoma dimerus. By double-label immunofluorescence, we first determined the association between NPY fibers and pituitary cells. In addition, we performed in vitro studies to evaluate the effect of NPY on GH and gonadotropins expression by real-time PCR, and release by Western blot, in males and females separately. Contacts between NPY fibers and GH and follicle-stimulating hormone (FSH)-producing cells were detected, indicating possible functional relationships. We observed an increase in GH release in the culture medium at 2 nM for males (p = 0.043) and 20 nM for females (p = 0.028). Pituitary FSH release was stimulated at 20 nM (p = 0.026) and 200 nM (p = 0.033) for males and females, respectively. Finally, NPY only increased β-LH mRNA expression at 20 nM in females (p = 0.028) and its release at 2 nM (p = 0.049) and 200 nM for males (p = 0.005) and 200 nM for females (p = 0.018). In conclusion, NPY acts as a GH-, LH- and FSH-releasing factor, in a dose- and sex-dependent way.

Interactions of Everolimus and Sorafenib in Whole Blood Lymphocyte Proliferation

Everolimus is an immunosuppressant that blocks growth factor-mediated proliferation of hematopoietic cells by targeting the mammalian target of rapamycin (mTOR). Sorafenib is a multikinase inhibitor that inhibits cell proliferation by arresting cells in the G0-G1 phase of the cell cycle. These agents are under investigation as combination therapy for various cancers. Because the two drugs individually inhibit lymphocyte proliferation, this study examined the effects of everolimus and sorafenib on lymphocyte proliferation in order to anticipate possible immunosuppression. Inhibition of lymphocyte proliferation was evaluated ex vivo over a range of concentrations of these drugs, alone and in combination. Data analysis, using a population approach to characterize interactions, employed the Ariens noncompetitive interaction model, which was modified to accommodate interactions of the two drugs. Everolimus alone caused partial inhibition of lymphocyte proliferation, with a mean IC(50) of 4.5 nM for females and 10.5 nM in males. Sorafenib alone caused complete inhibition, with a mean IC(50) of 11.4μM and no difference between genders. The population estimate for the interaction term was greater than 1, suggesting that the two drugs exert slight antagonism in terms of inhibition of lymphocyte proliferation.

Human brain contains a novel non-AT1, non-AT2 binding site for active angiotensin peptides

Aims To determine whether the novel non-AT1, non-AT2 binding site for angiotensins recently discovered in rodent brains occurs in the human brain. Main methods Radioligand binding assays of 125I-sarcosine 1, isoleucine 8 angiotensin II binding were carried out in homogenates of the rostral pole of the temporal cortex of human brains containing 0.3 mM parachloromercuribenzoate (PCMB), 10 µM losartan to saturate AT1 receptors, 10 µM PD123319 to saturate AT2 receptors, with or without 10 µM angiotensin II to define specific binding. Competition binding assays employed a variety of angiotensin peptides, specific angiotensin receptor antagonists, several neuropeptides and an endopeptidase inhibitor to determine pharmacological specificity for this binding site. Key findings The novel non-AT1, non-AT2 binding site was present in similar amounts in female and male brains: Bmax 1.77 ± 0.16 and 1.52 ± 0.17 fmol/mg initial wet weight in female and male brains, respectively. The K D values, 1.79 ± 0.09 nM for females, and 1.53 ± 0.06 nM for males were also similar. The binding site shows pharmacological specificity similar to that in rodent brains: sarcosine 1, isoleucine 8 angiotensin II > angiotensin III > angiotensin II > angiotensin I ’ angiotensin IV > angiotensin 1–7. Shorter angiotensin fragments and non-angiotensin peptides showed low affinity for this binding site. Significance The presence in human brain of this novel non-AT1, non-AT2 binding site supports the concept that this binding site is an important component of the brain angiotensin system. The functional significance of this binding site, either as a novel angiotensin receptor or a highly specific angiotensinase remains to be determined.

Seasonal changes in a ultraviolet structural colour signal in blue tits, Parus caeruleus

Recent studies of blue tits, Parus caeruleus, have found sexual selection and a viability-indicating function of the structural ultraviolet and blue crown plumage, but the reasons for this signal variation are not understood. Furthermore, studies in England and Sweden have yielded somewhat different results (particularly with regard to the spectral position of the reflectance peak). Here we investigate whether the blue tit UV/blue ornament varies with time of year since such variation might be relevant to the signalling function as well as the apparent difference between populations. From 400 blue tits captured at two different localities in Sweden, we found that objective measures of ‘hue’ (spectral location), ‘chroma’ (spectral purity) and ‘brightness’ (spectral intensity), varied substantially with season. Just after moult (October), crown ‘hue’ is maximally UV-shifted (359 nm for males and 373 nm for females). Thereafter the peak drifts upwards and by the time of nestling feeding (June) male reflectance peaks at 404 nm and female at 413 nm. This change is probably due to feather wear as well as fat and dirt accumulation, which might constitute an additional male quality cue. Our results suggest that it is important to consider plumage age when exploring variation in structural plumage coloration, and that it can largely explain the difference between the British and Swedish studies.

Abstract no.: 8 Endothelium‐dependent relaxation in atherosclerotic aorta segments of apolipoprotein E‐deficient (apoE‐/‐) mice

The present study investigated whether lesion‐free aorta segments of young apoE‐/‐ mice, which will later show endothelial dysfunction when atherosclerotic lesions develop, display normal endothelial function in comparison with ‘wild‐type’ (wt) C57Bl/6J mice. Endothelial function was assessed by studying endothelium‐dependent relaxation to acetylcholine (ACh) and concomitant elevations of endothelial internal calcium (Ca2+i). Therefore, atherosclerosis‐prone aorta strips were mounted in a myograph with the endothelial side down and loaded with fura2‐AM (340/380 excitation emission ratio in relative units, RU) to measure Ca2+i simultaneously with isometric force. In 90% of WT females (n = 10), 31% of WT males (n = 13), 100% of apoE‐/‐ females (n = 14) and 82% of apoE‐/‐ males (n = 11), relaxation of precontracted (1 μM phenylephrine, PE) strips by ACh (2 × 10−6 M) was accompanied by a contemporary increase of Ca2+i. ACh‐induced Ca2+i increase was not different between WT and apoE‐/‐ mice, but was greater in females than in males (0.14 ± 0.03 RU vs. 0.04 ± 0.03 RU, P &lt; 0.05). Dose‐response curves for ACh (10−9 to 3 × 10−6 M) revealed EC50‐values for ACh‐induced relaxations, which were significantly smaller in apoE‐/‐ than in wt (respectively 21 ± 7 nM vs. 61 ± 30 nM for females and 51 ± 22 vs. 82 ± 14 nM for males, P &lt; 0.05), pointing to a higher sensitivity of apoE‐/‐ segments to ACh. Except for wt males, in which relaxation seemed to be uncoupled from endothelial Ca2+i mobilization, EC50 values of ACh for calcium increase were similar for the three other groups (116 ± 47, 124 ± 16 and 117 ± 7 nM, respectively). It is concluded that before development of atherosclerotic lesions, apoE‐/‐ mice are more efficient than wt mice in transducing an increase of internal calcium upon muscarinic receptor stimulation into a nitric‐oxide dependent vasodilator response.

Characterization of a cytosolic estrogen receptor and its up-regulation by 17β-estradiol and the xenoestrogen 4 -tert-octylphenol in the liver of eelpout ( Zoarces viviparus)

Estrogen binding activity was revealed in the cytosolic fraction of hepatic extracts from adult male and female eelpout ( Zoarces viviparus). The binding moiety was characterized by a single class of high affinity binding sites ( K d=0.59±0.05 nM in males and 1.06±0.10 nM in females). The affinity was significantly higher in males. Binding sites were satiable and binding capacity was significantly elevated in vitellogenic females (2.92±0.28 pmol/g) compared to males (1.67±0.11 pmol/g). The binding was specific to known estrogens but not to other tested steroids. The binding moiety was able to bind to DNA–cellulose and was extractable by high salt concentrations. A time-course study of estrogen binding activity in liver cytosol and of vitellogenin (Vtg) in plasma, after intraperitoneal (i.p.) injections of 17β-estradiol (E 2) in male eelpout, was carried out. It was shown that both are inducible by E 2. Estrogen binding activity was significantly elevated 48 h and Vtg 72 h after E 2 treatment. The binding moiety was hereafter designated as a cytosolic estrogen receptor (ER). The estrogenicity of 4- tert-octylphenol (OP) was evaluated by measuring ER and Vtg after i.p. treatment. OP-treatment increased both receptor levels and Vtg concentrations in male fish, indicating that OP acts as an estrogen in male eelpout.

Spectral sensitivity in the eyes of male and female Lutzomyia longipalpis sandflies.

Using electroretinogram recordings, the response of Lutzomyia longipalpis sandfly eyes to a range of wavelengths of light was measured, and spectral sensitivity determined. The eyes of both male and female adult sandflies were found to respond maximally to light in the ultraviolet region (at 340 nm) with a secondary peak in the blue-green-yellow region at 520 nm for females and 546 nm for males. The Mann-Whitney U test showed no significant differences between males and females at corresponding wavelengths.

Dopamine receptors in human gastrointestinal mucosa

Dopamine is a putative enteric neurotransmitter that has been implicated in exocrine secretory and motility functions of the gastrointestinal tract of several mammalian species including man. This study was designed to determine the presence of dopamine binding sites in human gastric and duodenal mucosa and to describe certain biochemical characteristics of these enteric receptor sites. The binding assay was performed in triplicate with tissue homogenates obtained from healthy volunteers of both sexes using 3H-dopamine as a ligand. The extent of nonspecific binding was determined in the presence of a 100-fold excess of unlabeled dopamine. Scatchard analysis performed with increasing concentrations of 3H-dopamine (20–500 nM) revealed a single class of saturable dopamine binding sites in gastric and duodenal mucosa. Binding parameters obtained from the regression lines of the Scatchard plots of gastric mucosa of males were B max = 73.4±4.0 pmoles/mg protein; K D = 154±20 nM and B max = 95±13.6 pmoles/mg protein and K D = 826±200 nM in females. In duodenal mucosa of males these parameters were B max = 63.9±15.9 pmoles/protein; K D = 235±53 nM and B max = 83.2±19.4 pmoles/mg proteinK D = 568±104 nM in females. The results of this report demonstrate the presence of specific dopamine receptors in human gastric and duodenal mucosa. These biochemical data suggest that molecular abnormalities of these receptor sites may be operative in the pathogenesis of important gastrointestinal disorders. The view that the autonomic innervation of the mammalian gastrointestinal tract is provided by parasympathetic (cholinergic) excitatory and sympathetic (adrenergic) inhibitory fibers has been expanded by the findings that these fibers contain not only acetylcholine and norepirephrine, but also several other aminergic and peptidergic neurotransmitters (1,2). Immunohistochemical studies have shown, for example, that the vagus nerve (in addition to acetylcholine) contains important amounts of serotonin, norepinephrine, gastrin, somatostatin, enkephalin, substance P and vasoactive-intestinal peptide (3). These findings suggest that the neural control of the gut is considerably more complex than originally thought, and raise the possibility that exocrine secretory and motility functions of the gut may be regulated by multiple enteric neurotransmitters. Recent evidence suggests that dopamine may be an important transmitter in enteric synapses, as well as a precursor molecule in the biosynthesis of norepinephrine in peripheral adrenergic terminals (4). Although, specific immunohistochemical demonstration of tyrosine hydroxylase in gastric tissue has not been provided, significant amounts of dopamine have been found in the gastrointestinal mucosa and muscle of several mammalian species (5) and in human gastric juice (6,7). In addition, it is also important to indicate that DOPA decarboxylase activity has been detected in a specific enterochromaffin-like cell system in the gastric mucosa (8). There is also evidence that dopamine levels in gastric mucosa but not in muscle are regulated independently of either parasympathetic or sympathetic control (9). Furthermore, neurophysiological studies indicate that dopamine, like norepinephrine, exerts an inhibitory effect on cholinergic neurotransmission by including hyperpolarization of the post-synaptic membrane (10). Inhibitory actions of dopamine and dopamine-related compounds on acid secretion (11–14), gastric emptying (15), antral activity (16), and intragastric pressure have been demonstrated in rats, dogs and man (17). Specific high-affinity dopamine receptors and different molecular species of these receptor sites have been extensively studied in rat and human brain tissue (18,19). Similar, but less extensive studies, have been performed with gastrointestinal tissue. Szabo et al. (20) provided an initial description of dopamine receptors in rat stomach and duodenum, and suggested that they may be involved in the pathogenesis of experimental duodenal ulceration. More recently, we have provided a detailed biochemical characterization of specific receptor sites for dopamine in rat gastric mucosa and muscle and suggested that these molecular entities may play a critical role in the onset of stress ulcers (21). This body of evidence indicates that dopamine and dopamine receptors may play an important role in gastrointestinal physiology and suggest that similar dopamine receptors may also be present in human gastrointestinal tissue. The study described below was specifically designed to determine the presence of dopamine binding sites in human gastric and duodenal mucosa.

Increased insulin sensitivity and responsiveness of glucose metabolism in adipocytes from female versus male rats.

This study was undertaken to examine whether there were sex-associated differences in the action of insulin on glucose metabolism in adipocytes. Insulin binding and the dose-response curves for glucose transport (assessed by measuring the cell-associated radioactivity after 15-s incubation with 50 microM [6-14C]glucose) and [U-14C]glucose (5 mM) metabolism into CO2 and lipids were compared in retroperitoneal adipocytes from age-matched (84 d) male and female rats. In addition, the activity of fatty acid synthetase, one of the key lipogenic enzymes, was determined. Fat cell size was not significantly larger in females than in males (0.238 vs. 0.209 microgram lipid per cell). At insulin concentrations less than or equal to 1.6 nM, adipocytes from females bound significantly more insulin than did adipocytes from males, due to an increased apparent affinity of the receptors for insulin. Accordingly, the sensitivity of glucose transport to insulin was greater in females than in males: insulin concentration eliciting half-maximal stimulation (ED50) = 0.19 nM vs. 0.41 nM. At maximal insulin stimulation the rates of glucose transport (12 times the basal values) were similar in the two sexes. In contrast, the maximal effect of insulin on glucose conversion to CO2 plus lipids was much greater in the adipocytes from females than males (increment over basal: 472 vs. 249 nmol/10(6) cells per 2 h). Fatty acid synthesis contributed approximately 40% of the incremental difference between the two types of adipocytes, while glyceride-glycerol synthesis contributed less than 10%. The insulin dose-response curves for adipocytes from females were shifted to the left for all the metabolic pathways investigated. The mean ED50 for total glucose metabolism in females was 50% of that in males (0.07 nM vs. 0.15 nM). Marked sex-associated differences in the action of insulin on glucose metabolism were also observed in subcutaneous inguinal adipocytes (increment over basal: 137 and 56 nmol/10(6) cells per 2 h, ED50 = 0.13 nM and 0.30 nM in females and males, respectively). The intracellular capacity to metabolize glucose through the fatty acid synthesis pathway, as assessed by FAS activity, was higher in adipocytes from females than in those from males and was greater in retroperitoneal than in inguinal adipocytes. Furthermore, by plotting the individual data, a highly significant correlation (r = 0.92, P less than 0.001) was found between the absolute effect of insulin on glucose metabolism at maximal stimulation and the fatty acid synthetase activity of the cells. These results indicate that the response of glucose metabolism to insulin in adipocytes from female as compared with male rats is characterized by two main features: (a) an increased sensitivity primarily due to an increase in insulin binding, and (b) an increased responsiveness closely associated with a postreceptor increase in the lipogenic capacity of the cell. These findings might be relevant to the differential disposition of male and female rats to develop fatness.

The measurement of 4-androstene-3,11,17-trione (11-oxo-androstendione) by radioimmunoassay in human plasma

A radioimmunoassay (RIA) method is described for the determination of 4-androstene-3,11,17-trione (11-oxo-androstendione) in human plasma. 4-androstene-3,11,17-trione 3-(0-carboxymethyl) oxime-bovine serum albumin conjugate was used to generate highly specific antiserum in rabbits. Cross reactivities of several other steroids with the antiserum were less than 4%. [1,2- 3H] 4-androstene-3,11,17-trione was synthesized from [1,2- 3H] 17α,21-dihydroxy-4-pregnene-3,11,20-trione. The intra- and interassay variation was 7.3% and 9.8%, respectively. The mean serum 4-androstene-3,11,17-trione level for healthy young subjects was 2.37 ± 0.56 nM (x ± SD) in males and 3.16 ± 0.43 nM in females at 8 a.m. During the night, there was a marked decrease in serum level, giving at 11 p.m. 0.87 ± 0.33 and 1.15 ± 0.52 nM, respectively. During ACTH stimulation tests, 4-androstene-3,11,17-trione increased from 1.81 ± 0.58 to 2.32 ± 0.69 nM, while in dexamethasone suppression tests a decrease from 3.20 ± 0.03 nM was seen. In contrast, HCG administration on 3 consecutive days did not influence plasma concentrations of 4-androstene-3,11,17-trione.