Demonstration and partial characterization of cytosol receptors for testosterone

Structural study and expression of the androgen receptors during the reproductive cycle in the Harderian gland of the male Meriones libycus

The goal of this study was to evaluate for the first time the expression of the androgen receptors (AR) in Harderian glands (HG) of the male Meriones lybicus in relation to the reproductive cycle. Six male Harderian glands of the resting period and 6 of the breeding period were collected. The animals were trapped in the desert of Béni Abbès (Algeria). The morphology of the Harderian glands was studied by light microscopy and morphometry, whereas the expression of the androgen receptors was assessed and quantified based on immunohistochemistry techniques. We have shown that the Harderian glands of Meriones libycus are tubuloalveolar glands with wide lumen. The glandular epithelium is composed of two types of cells (types I and II) in the resting season and three types of cells (types I, II and III) in the breeding season. These three types of cells differ in size and shape. Type-I cells have a prismatic shape, an acidophilic cytoplasm, and small lipidic vacuoles, whereas type-II ones are pyramidal in shape, with basophilic cytoplasm. Type-III cells resemble those of type I, and so they are prismatic in shape and have an acidophilic cytoplasm with larger lipidic vacuoles. The immunoreactivity of type-I and type-III cells was mainly cytoplasmic and the intensity of the immunostaining was significantly higher during the breeding season. Among other functions, the Harderian gland seems to be involved in the production of pheromones under the effect of androgens.

Sex-based differences in skeletal muscle kinetics and fiber-type composition

Previous studies have identified over 3,000 genes that are differentially expressed in male and female skeletal muscle. Here, we review the sex-based differences in skeletal muscle fiber composition, myosin heavy chain expression, contractile function, and the regulation of these physiological differences by thyroid hormone, estrogen, and testosterone. The findings presented lay the basis for the continued work needed to fully understand the skeletal muscle differences between males and females.

Fostering in mice induces cardiovascular and metabolic dysfunction in adulthood

Cross-fostering is widely used in developmental programming studies to determine the relative contribution of the in utero and suckling periods in establishing the adult offspring phenotype in response to an environmental challenge. We have investigated whether the process of fostering per se influences cardiovascular and metabolic function in adult offspring of C57BL/6J mice in comparison with animals suckled by their biological dams. Cross-fostered (CF) mice demonstrated juvenile onset hyperphagia and significantly higher body weight (from weaning to 12 weeks: male control (CON) vs. CF: P < 0.01, female CON vs. CF: P < 0.001; RM ANOVA) accompanied by increased abdominal adiposity in males only (white adipose tissue mass (mg): CON 280.5 ± 13.4 [mean ± SEM] (n = 7) vs. CF, 549.8 ± 99.3 (n = 8), P < 0.01). Both male and female CF mice demonstrated significantly enhanced glucose tolerance. A marked increase in systolic blood pressure (SBP) was observed in male CF mice (SBP (mmHg), day: CON 100.5 ± 1.4 (n = 6) vs. CF 114.3 ± 0.7 (n = 6), P < 0.001; night: CON 108.0 ± 2.0 (n = 6) vs. CF 123.2 ± 1.1 (n = 6), P < 0.001). Endothelium-dependent relaxation was enhanced in male CF mice, and renal noradrenaline was increased in female CF mice. Concentration of serum triglycerides, cholesterol, insulin and leptin were increased in CF vs. CON. The process of cross-fostering profoundly affects cardiovascular and metabolic phenotype in mice. The findings have implications for the inclusion of appropriate controls in the design of future studies and in the interpretation of previous cross-fostering studies in mice.

Non-classical actions of testosterone: an update

Androgens are known to exert their effects via genomic signalling, which involves intracellular androgen receptors that modulate gene expression on steroid binding. Whereas non-classical estrogen effects are well established, it is only recently that non-classical, rapid, membrane-initiated testosterone actions have received attention. Non-classical effects of testosterone have now been demonstrated convincingly in several tissues, in particular in the reproductive, cardiovascular, immune and musculoskeletal systems. There is evidence for the participation of the classical intracellular androgen receptor and for involvement of novel, membrane-associated androgen receptors in the non-classical actions of testosterone. Here we discuss evidence for rapid testosterone actions, which have clinical implications in fertility, cardiovascular disease and the treatment of prostate cancer.

Effects of experimental diabetes on the structure and ultrastructure of the coagulating gland of C57BL/6J and NOD mice

Diabetes mellitus can lead to reproductive disorders that in turn result in weakened fertility brought about by morphofunctional changes in the testes and accessory sex glands. However, doubts persist concerning the basic biology of the secretory epithelial cells and the stroma of the coagulating gland of diabetic mice. Thus, the objective of the present study was to analyze the histological and ultrastructural changes associated with stereology of the coagulating gland of mice with alloxan-induced diabetes, and of spontaneously diabetic mice. Sixteen mice of the C57BL/6J strain, and eight non-obese diabetic (NOD) mice were used. The animals were divided into three groups: 1) control (C), 2) alloxan diabetic (AD), and 3) NOD. Thirty days after the detection of diabetic status in group 2, all of the animals were killed and then perfused with Karnovsky's solution through the left cardiac ventricle. The coagulating gland was then removed and processed for morphometric study by light microscopy and electron microscopy. The results showed thickening of the stroma, atrophy of secretory epithelial cells, and disorganization of the organelles involved in the secretory process in both NOD and alloxan-induced mice. Thus, it may be concluded that the coagulating gland suffered drastic morphological changes, and consequently impaired glandular function, in the presence of diabetes mellitus type I in both NOD and AD mice.

Contribution of androgens to chronic allograft nephropathy is mediated by dihydrotestosterone

BACKGROUND

Donor and recipient gender influence long-term allograft outcome after kidney transplantation. Sex hormones are likely to contribute to these gender-related differences. The present study investigated the role of androgens and their inhibition on the development of chronic allograft nephropathy.

METHODS

Male or female Fisher (F344) kidneys were orthotopically transplanted into intact male Lewis recipients. Animals were treated either with testosterone, the antiandrogen flutamide, the 5alpha-reductase inhibitor finasteride, or vehicle. Twenty weeks after transplantation animals were harvested for histology, immunohistology, and molecular analysis.

RESULTS

Testosterone treatment resulted in an increased proteinuria as well as profound glomerulosclerosis, tubulointerstitial fibrosis, and mononuclear cell infiltration that paralleled enhanced intragraft mRNA levels of transforming growth factor-beta (TGF-beta) and platelet-derived growth factor-A and -B chain (PDGF-A and -B). In contrast, flutamide and finasteride reduced glomerulosclerosis as well as the inflammatory cell infiltration associated with decreased TGF-beta, PDGF-A, and -B chain mRNA expression. No gender-related donor differences were noted between the groups.

CONCLUSIONS

Our data suggest that dihydrotestosterone mediates the adverse effects of androgens on chronic allograft nephropathy. The inhibition of androgens improves long-term allograft outcome after kidney transplantation.

Recombinant expression and purification of human androgen receptor in a baculovirus system

A full-length human androgen receptor (hAR) cDNA was used to produce recombinant baculovirus. Spodoptera frugiperda (Sf9) cells infected with this virus expressed protein with an N-terminal hexahistidine tag (His(6)-hAR) in soluble and insoluble forms. The soluble cytosolic His(6)-hAR demonstrated similar association and dissociation half-times for mibolerone, similar binding affinity for mibolerone, and similar steroid specificity as bona fide AR. Under native conditions, the soluble cytosolic His(6)-hAR was purified to apparent homogeneity in the presence of dihydrotestosterone, using metal ion affinity chromatography. The insoluble pellet fraction was solubilized with strong denaturant 6 M guanidine HCl, and His(6)-hAR was purified from it in the presence of 6 M guanidine HCl. Both the solubilized crude pellet fraction and the solubilized/purified His(6)-hAR could be renatured to bind mibolerone. The baculovirus system will therefore provide an efficient means for producing hAR for ligand-binding assays, as well as purifying hAR for detailed molecular analyses.

Hormones and the control of porphyrin biosynthesis and structure in the hamster harderian gland

The hamster Harderian gland seems to present both an excellent model for the control of porphyrin biosynthesis and an unusually robust example of the interrelationship between structure and function. It has been known for some time that 1) the capacity for manufacturing and storing porphyrins and 2) gland histology and ultrastructure are controlled by androgens. Thus, in intact males as well as in gonadectomised animals of either sex treated with androgens, porphyrin synthesis by the Harderian gland is suppressed and the gland tubules characteristically possess two cell types, the cytoplasm of both containing polytubular complexes. By contrast, the Harderian glands of intact females and castrated males synthesise and store large amounts of protoporphyrin, while their tubules possess only one cell type which lacks a polytubular complexes. So overarching is the effect of androgens that they have been described as a "coarse tuning" effect on the gland. By contrast, the role of the ovary is both less dramatic and less well understood. In female hamsters, ovariectomy leads to degenerative changes in Harderian gland tubules and (probably) a release of stored porphyrin; at the same time there is a reduction in enzyme levels and new synthesis. The causative hormone in this "fine tuning" is unclear at present. There is now clear evidence that the Harderian gland is also controlled directly by pituitary hormones. In particular, the use of continuous infusion osmotic minipumps has allowed us to demonstrate not only 1) that the expected rise in porphyrins and feminisation of gland morphology does not occur in castrated males receiving the dopamine agonist bromocriptine, but that 2) the simultaneous administration of prolactin does permit these changes; furthermore, 3) the administration of prolactin alone increases porphyrin synthesis above the levels found in untreated castrates. Similarly, bromocriptine administration to ovariectomised females markedly reduces porphyrin synthesis and masculinises gland structure; again, this is reversed by the simultaneous administration of prolactin. Prolactin must therefore be seen as equipotent with androgens in determining gland structure and activity.

The effects of bromocriptine and prolactin on porphyrin biosynthesis and morphology in the female hamster harderian gland

Porphyrin biosynthesis was examined in the Harderian gland of the female golden hamster by fluorometric assays of gland porphyrin content and by measuring the activity of a rate-limiting enzyme for haem biosynthesis, delta-aminolaevulinic acid synthase. Both porphyrin content and enzyme activity are high in normal female glands. Enzyme activity was lowered in females ovariectomised for 6 weeks, and both enzyme activity and porphyrin content were greatly lowered in ovariectomised females given the dopamine agonist bromocriptine; this suppression could be prevented by simultaneous prolactin administration. Bromocriptine (but not ovariectomy alone) also masculinised the morphology of the Harderian gland, resulting in the appearance of type II cells and polytubular complexes; again, the simultaneous administration of prolactin prevented masculinisation. The results support the hypothesis that while androgens have an inhibitory effect on porphyrin synthesis within this model, prolactin may have a major facilitatory role.

Effect of testosterone on purine metabolism and morphometric parameters in the rat liver

The effect of testosterone on the morphology and biochemistry of adult castrated rat liver is described. Castration decreases mean weight and volume of hepatocytes, volume and surface area of sinusoidal lumen, and apparently increases cell number per g of tissue. These variations indicate cell distress. Testosterone administration restored sinusoidal volume and surface area, indicating a true hyperplastic response and improved trophic conditions. Acid soluble nucleotides, RNA and DNA content were lower after castration, being partially restored after testosterone treatment. This restoration, however, was only statistically significant for total guanylate. We concluded that testosterone deficiency and administration exerts a specific effect on the liver in terms of morphological and biochemical changes. Purine nucleotide metabolism is probably the first target of hormonal action, since its changes are the most significant and useful to explain all the other observations.

Effects of 17 beta-oestradiol and 5 alpha-dihydrotestosterone on the expression of the muscle and heart types of lactate dehydrogenase isozymes in the masseter muscle of developing mice

17 beta-oestradiol (E2) and/or 5 alpha-dihydrotestosterone (5 alpha-DHT) had no effect on the expression of isozymes of lactate dehydrogenase (LDH) in the masseter muscle of intact male mice. However, treatment with E2 restored the level of the muscle (M) type of LDH isozyme, which had been reduced by testectomy, to that found in intact male mice treated with vehicle only. Moreover, 5 alpha-DHT alone was more effective than E2 in increasing the relative level of this isozyme in testectomized mice. 5 alpha-DHT had a more significant effect on the increase in the relative level of the M-type LDH isozyme when combined with E2. These results suggest that androgens promote, in the presence of oestrogens, the postnatal changes in the characteristics of the masseter muscle of developing male animals.

Androgen regulation of gene expression in the Syrian hamster Harderian gland

The androgenic control of sexual dimorphism has been studied in the Harderian gland from Syrian hamster and compared to rat Harderian gland, a system without dimorphism. Hybridization in situ with a rat cDNA clone has revealed the presence of androgen receptor mRNA in all secretory cells from male and female hamster glands. Testosterone or 5-alpha-dihydrotestosterone administration to females both caused a 60% decrease in the levels of 5-aminolevulinate synthase mRNA after 1 day of treatment, but the resulting patterns of in vitro translation using RNA from glands treated with the two androgens are different. Testosterone alters the mRNA levels for androgen receptor and 5-aminolevulinate synthase in the glands only 6 h after its implantation in females, and the action is maintained up to 10 days of treatment. Finally, androgen administration to females or deprivation in males alter androgen receptor but not 5-aminolevulinate synthase mRNA levels in rat Harderian glands. Our results suggest that the androgen receptor from Harderian glands is responsible for the sexual dimorphism found in Syrian hamsters, whereas the lack of sexual dimorphism in rat seems to be due to a restricted effect of androgens in the glands.

Human androgen receptor expressed in HeLa cells activates transcription in vitro

The androgen receptor (AR) is a ligand-responsive transcription factor, belonging to the class of steroid receptors. AR mutations have been associated with various X-linked diseases, characterized by complete or partial resistance to androgens. To further analyse the molecular mechanism of action of the AR, we have produced the human AR in HeLa cells with a Vaccinia virus expression system. Binding studies on infected HeLa cells demonstrate that the recombinant AR interacts specifically and with high affinity with natural and synthetic androgens. In a gel retardation assay the partially purified AR specifically recognizes an androgen response element of the rat prostatic binding protein gene. Moreover, the recombinant AR activates transcription in vitro from a synthetic promoter construct containing glucocorticoid response elements (GRE).

DNA-binding of androgen receptor overexpressed in mammalian cells

In order to investigate the DNA-binding properties of the rat androgen receptor (rAR) in mammalian cells after addition of androgens and antiandrogens, we established a gel-shift assay with extract from COS-1 cells (CV-1 cells transformed with the DNA-tumour virus SV40) over-expressing the rAR. First, the rAR was overexpressed in COS-1 cells. Therefore the full-length AR cDNA was inserted immediately downstream from the SV40 early promoter of pECE to generate pECE-AR. Expression of the rAR driven by the SV40 early promoter yields constant and high levels of rAR protein. In addition, the vector contains the SV40 origin of replication for obtaining high copy vector numbers in COS-1 cells. The rAR-containing expression vector was transiently transfected into COS-1 cells using Transfectam Reagent, in order to achieve high transfection efficiency. Expression of biologically active receptor was tested by analyzing the effect of the synthetic androgen R1881 on induction of transiently transfected pMMTV-CAT. Steroid binding assays were carried out to confirm overexpression of biologically active AR and to determine the binding of different hormones and antihormones to AR in COS-1 cells transiently transfected with pECE-AR. Gel-shift experiments performed with whole cell extract of those cells, containing approximately 700 fmol AR/mg protein, and labeled AR-binding GRE (glucocorticoid responsive element) showed that R1881 induced the formation of a protein-GRE complex. Furthermore, the R1881-induced formation of the protein-GRE complex could be completed by addition of unlabeled excess of GRE but not of unspecific oligonucleotides, confirming sequence-specific binding of the R1881-induced protein-GRE complex.

Characterization of human androgen receptor overexpressed in the baculovirus system

An essential step in the process of understanding the structure and function of the human androgen receptor (hAR) involves the production of large quantities of the hAR. For this purpose, the full-length hAR has been overproduced in insect cells by using a baculovirus genetic expression system. The recombinant hAR is produced in Sf21 insect cells at approximately 7 pmol/mg of protein (1 x 10(6) AR molecules per cell), which is 70-150 times greater than levels detected in androgen target tissues. Androgen can bind to the baculovirus-expressed hAR with high affinity (Kd = 0.46 nM), and the specificity of hormone binding in baculovirus-expressed hAR is essentially identical to that of bona fide hAR. An anti-AR monoclonal antibody can recognize the baculovirus-expressed hAR at approximately 100 kDa upon Western blot analysis. Sucrose gradient analysis shows that baculovirus-expressed hAR complexes sediment at 4 S in a high salt medium and these complexes can interact with anti-AR monoclonal antibody to form complexes that sediment at 8-10 S. Therefore, production of recombinant hAR from the baculovirus expression system will provide an alternative source of biologically active hAR for studies on the molecular mechanisms of androgen action.

Comparison of changes in testosterone concentrations after strength and endurance exercise in well trained men

Changes in the testosterone concentrations after single sessions of endurance and strength training were measured in seven well trained men, experienced in both forms of training. Both training sessions were rated as hard to very hard on the Borg scale. Blood samples for testosterone measurements were taken before, immediately after, and 2, 4 and 6 h after the training sessions as well as the next morning. The mean testosterone concentration increased 27% (P less than 0.02) and 37% (P less than 0.02) during the strength and endurance training session, respectively. Two hours after the training sessions the mean testosterone concentration had returned to the pre-training level and remained at that level for the length of the observation period. There were no significant differences in the changes in testosterone concentration after strength and endurance training but there were large differences in the testosterone response at the level of the individual. A high correlation (r = 0.98; P less than 0.001) for individuals was found between increases in testosterone concentration after strength and after endurance training. It was concluded that the changes in mean testosterone values followed the same timecourse after single sessions of strength and endurance training of the same duration and perceived exertion. The interindividual differences in testosterone response may be of importance for individual adaptation to training.

Harderian glands of golden hamsters: morphological and biochemical responses to thyroid hormones

Manipulation of circulating levels of thyroid hormones modifies Harderian gland structure and porphyrin concentrations in male and female golden hamsters. Specifically, thyroxine (T4) and triiodothyronine (T3) induce the morphological conversion of the Harderian glands of females to approximate those of the male. Further, porphyrin concentrations are markedly decreased by this treatment. This effect occurs in ovariectomized animals as well, indicating that the gonads are not involved. Suppression of thyroid function by potassium perchlorate (KClO4) drastically reduces Harderian gland weight in both males and females. However, KClO4 decreases porphyrin levels in the Harderian glands of females and increases it in the male. Concurrently, KClO4 also induces a morphological conversion of the Harderian glands of males to the female type. This effect is evident in photoperiods of either 14:10 (h) or 8:16 (h).

Hormonal control of muscle growth

In muscle of whole animals, pituitary growth hormone, the thyroid hormones, and insulin are major growth-promoting hormones, and the glucocorticoids have significant catabolic actions. At the cellular level the primary anabolic hormones for cultured myoblasts are the somatomedins (insulin-like growth factors) and fibroblast growth factor. In these cells physiological concentrations of growth hormone, thyroid hormones, and insulin have no growth-promoting effect; some of the reported actions of insulin probably result from cross-reaction with the somatomedin receptor. Results with purified proteins do not support the view that mitogens block myoblast differentiation; transforming growth factor-beta and interferon are nonmitogenic proteins that inhibit differentiation, insulin-like growth factors are mitogens that stimulate differentiation, and fibroblast growth factor is the only purified mitogen that inhibits differentiation. At least six serum-free media have now been devised for the growth of various kinds of muscle cells under closely defined conditions.

Application of high-performance liquid chromatofocusing to the study of prostatic androgen receptors. Effect of stabilizing agents on the heterogeneity of receptor structure

Cytosolic androgen receptors from normal rat prostate were analyzed by high-performance liquid chromatofocusing. Two ion-exchange columns, AX-300 and AX-500, and two equilibration systems, Tris-HCl and imidazole-HCl, were used. pH gradients ranged between 8.3 and 3.5 for Tris-HCl and from 7.7 to 3.5 for imidazole-HCl. In the absence of sodium molybdate and inhibitors of proteolytic enzyme, six specific radioactive fractions (pH: 7.9, 7.7, 7.0, 5.1, 4.7 and 4.4) were eluted from AX-300 equilibrated with Tris-HCl in a ratio of 28:20:52 for acidic, intermediary and basic forms, respectively; similar results were obtained with AX-500 although this column was less effective in resolving basic forms of the receptor. The buffering capacity of imidazole-HCl was lower than that of Tris-HCl, resulting in a steeper elution pH profile. The resolution between acidic and basic forms was thus diminished and only four specific radioactive fractions at pH 7.2, 7.1, 6.5 and 3.6, were observed on AX-500 in a ratio of 23:10:67 for acidic, intermediary and basic forms. In the presence of sodium molybdate, two acidic fractions were found with Tris-HCl at pH 4.3 and 4.7 (47%) on AX-300, whereas the radioactivity of fractions at pH 7.0 and 5.1 (32%) was considerably lowered and intermediary forms remained unchanged (21%). With imidazole-HCl on AX-500, the peak at pH 7.2 disappeared and the acidic form shifted from pH 3.6 to 4.3. In the presence of inhibitors of proteolytic enzyme and sodium molybdate, specifically bound radioactivity was found mostly in a broad acidic fraction (75%) at pH 4.5 on columns equilibrated with Tris-HCl; radioactivity at pH 7.6 disappeared completely but a small amount (15%) remained at pH 7.9. In imidazole-HCl, a main radioactive fraction was eluted at pH 7.1 and two other fractions were collected at pH 6.8 and 4.3 respectively. In conclusion, multiple forms of the rat prostate androgen receptor were evinced by high-performance liquid chromatofocusing. Tris-HCl proved to be a more efficient equilibration system than imidazole-HCl for the resolution of rat prostate cytosolic binding proteins. Under the experimental conditions used, sodium molybdate and inhibitors of proteolytic enzyme greatly favored the acidic form to the detriment of the intermediary and basic entities.

Mouse monoclonal antibodies against rat estramustine binding protein

Hybridomas producing antibodies against rat prostatic estramustine binding protein (rEMBP) have been obtained by fusion of spleen lymphocytes from Balb/c mice, immunized with rEMBP, and SP2/0 Ag 14 mouse myeloma cells. Anti-rEMBP IgG producing cultures were identified in a solid phase ELISA using alkaline phosphatase conjugated sheep antimouse IgG. Cultures producing specific antibodies were subcloned and expanded. The produced immunoglobulins were characterized according to interaction with subunits of rEMBP. No interaction was found with [3H]estramustine-human estramustine binding protein. Following development of a radioimmunoassay, tissue distribution of rEMBP in the rat was studied. Despite high specificity, shown by selective interaction with rEMBP (F and S subunits), macromolecules interacting with anti-rEMBP were found in high concentrations in the prostrate and also in low concentrations, in other tissues of the male genital tract, and further in the adrenals, pancreas and submaxillary gland. The high specificity also makes it possible to study the F and S subunit selectively. These results show that macromolecules very similar to rEMBP are present in hormone-sensitive tissues in the rat.

Long-term effects of estrogen on rat skeletal muscle

The long-term effects of estrogen on the development of rat extensor digitorum longus (EDL) and soleus (SOL) muscles were examined using physiological and histochemical methods. The rats were in three groups: group 1, ovariectomized; group 2, sham-operated; and group 3, ovariectomized followed by estradiol administration. Isometric twitch and tetanic tensions of both the EDL and SOL obtained from 10-week-old rats were evoked by electrical stimulation. The isometric twitch tensions of the EDL in groups 2 and 3 were significantly lower than in group 1, however, there was no significant differences in isometric twitch tensions of the SOL among the three groups. The isometric tetanic tensions of the EDL in groups 2 and 3 were also significantly lower than in group 1, and the isometric tetanic tension of the SOL in group 3 was significantly lower than in group 1. There were no changes in the total number of muscle fibers or in the ratios of fiber types. But the mean fiber diameter of all fiber types (particularly in types IIA and IIB) was significantly lower in group 3 than in groups 1 and 2. Therefore, the possibility that estrogen may play an inhibitory role in the development of skeletal muscle fibers has to be considered.

Androgen cytosol binding in exercise-induced sparing of muscle atrophy

This study was undertaken to determine whether the exercise-induced sparing of glucocorticoid-induced muscle atrophy is related to increased androgen cytosol binding. Female rats were divided into a sedentary or an exercise group that was trained by treadmill running 100 min/day for 13-15 wk. During the last 12 days of training, each of these groups was further subdivided into groups that received daily subcutaneous injections of cortisone acetate (CA) (100 mg/kg body wt) or the vehicle 1% carboxymethyl cellulose. Exercise prevented 30-40% of the weight loss due to CA treatment in gastrocnemius and plantaris muscles. Scatchard analyses of specific binding of [3H]methyltrienolone (R1881), a synthetic androgen that binds to androgen receptors, were nonlinear in muscles from vehicle-treated sedentary and trained rats and were resolved by a two-component binding model. The lower affinity component, which was attributed to a glucocorticoid receptor, disappeared in muscles of glucocorticoid-treated animals as evidenced by linear Scatchard plots. Receptor concentrations of the androgenic component of [3H]methyltrienolone binding were similar in gastrocnemius and plantaris muscles in all treatment groups. In binding specificity studies of gastrocnemius muscles, the relatively high competition by various glucocorticoids and progesterone for [3H]methyltrienolone binding in the vehicle-treated groups was reduced by CA treatment. The lack of change in androgen cytosol receptor levels suggests that this is not a mechanism by which exercise protects against glucocorticoid-induced muscle atrophy.

Skeletal muscle cytosol [3H]methyltrienolone receptor binding and serum androgens: effects of hypertrophy and hormonal state

Normal, castrated, and hypophysectomized male rats underwent compensatory hypertrophy of plantaris muscles following surgical removal of their synergistic gastrocnemius muscles. The increases in muscle wet weights above control values, determined when the muscles were in stable-state hypertrophy, were as follows: normal 50%, castrated 50%, and hypophysectomized 32%. There were marked differences in concentration of serum androgens between surgical groups, yet no increases in testosterone or 5 alpha-dihydrotestosterone were observed as a result of hypertrophy. The amount of testosterone binding to serum proteins (approx 94%) was reduced only in hypophysectomized animals that underwent muscle growth. Cytosol androgen receptor specific binding (fmol/mg protein), measured using saturating concentrations of [3H]methyltrienolone (R1881) at 4 degrees C for 20 h for exchange with endogenous steroid, was significantly increased in hypertrophied muscles of normal, (1.77 +/- 0.17 vs 1.16 +/- 0.21), castrated (2.27 +/- 0.20 vs 1.46 +/- 0.03) and hypophysectomized (6.23 +/- 0.56 vs 3.64 +/- 0.30) animals. Receptor dissociation constants (Kd) were approx 10(-10) M in all groups and were not altered by the hypertrophy. These findings show that a major adaptation to skeletal muscle enlargement is an augmentation of cytosol [3H]methyltrienolone receptor binding capacity. This effect occurs in a normal or androgen deficient state.

Detection of conformational changes in chloroplast coupling factor 1 by 8-anilino-1-naphthalene-sulphonate fluorescence changes

Chloroplast coupling factor 1 (CF1) contains a high-affinity binding site for 8-anilino-1-napthalene sulphonate (ANS,Kd = 5-6 microM). The binding of ANS to the enzyme is associated with a fluorescence enhancement and a blue-shift in the emission spectrum. ANS only slightly inhibits ATP hydrolysis by CF1. Adenine nucleotides and inorganic phosphate induce a fast ANS fluorescence quenching of about 50% which is due to a decrease in the affinity of the enzyme for ANS (Kd increases from 6 microM to 22 microM) and in the fluorescence quantum yield of the bound probe (by 33%) but not in the number of ANS sites (n = 1). Conversely, Mg and Ca ions induce a fluorescence enhancement of bound ANS. Inactivation of the enzyme enhances ANS fluorescence, eliminates the response to adenine nucleotides and inorganic phosphate but increases the response to divalent metals. The affinity of latent CF1 for ADP (Kd = 12 microM) is considerably higher than for ATP (Kd = 95 microM) in buffer containing EDTA. The Kd for inorganic phosphate is 140 microM. Mg increases the apparent affinity for ATP (Kd = 28 microM) but not for ADP or Pi. Binding of ATP to the tight-sites does not inhibit the ADP or Pi-induced fluorescence quenching but decreases the affinity for ADP (Kd = 34 microM) and for inorganic phosphate (Kd = 320 microM). These results suggest that the ADP and phosphate binding sites are different but not independent from the tight sites. Activation of a Mg-specific ATPase in CF1 by octyl glucoside decreases the affinity for ADP and inorganic phosphate by about threefold but increases the affinity for ATP. ATPase activation of CF1 also increases the Ki for ADP inhibition of ATP hydrolysis. ATPase activation also influences the ANS responses to Ca and Mg. Ca-ATPase activation increases the fluorescence enhancement and the apparent affinity for Ca whereas Mg-ATPase activation specifically increases the Mg-induced fluorescence enhancement. The fluorescence of CF1-bound ANS is enhanced by Dio-9 and quenched by phloridzin, quercetin, Nbf-Cl and FITC. Nbf-Cl and FITC completely inhibit the ADP-induced fluorescence quenching whereas Dio-9 inhibits the Mg-induced fluorescence enhancement. ANS does not relieve the quercetin or phloridzin inhibition of ATP hydrolysis indicating that these inhibitors do not compete with ANS for a common binding site. ANS may be used, therefore, as a sensitive probe to detect conformational changes in CF1 in response to activation or inactivation and to binding of substrates and of inhibitors.

Effect of castration on the metabolism of androgens in rat skeletal muscle

The metabolic conversion of testosterone and 17 beta-hydroxy-5 alpha-andro-stan-3-one by cell fractions from skeletal muscle was examined. Little or no conversion of testosterone to 17 beta-hydroxy-5 alpha-androstan-3-one is observed with any skeletal muscle fraction studied. The cytosol from all muscles examined contained substantial levels of the enzyme 3 alpha-hydroxysteroid oxidoreductase, which converts 17 beta-hydroxy-5 alpha-androstan-3-one to 5 alpha-androstane-3,17 beta-diol. The Km of the reaction in the three muscles (extensor digitorum longus, soleus and levator ani) is in the order of 3-6 X 10(-6) M. Following castration, there is no significant change in the Km value of this reaction in any of the muscles. The Vmax of the conversion in the extensor digitorum longus and soleus are similar (in the order of 2.0 X 10(-11) mol/mg per min) and castration has no significant effect on Vmax in either of these muscles. Vmax is significantly lower for the levator ani (3.4 X 10(-12) mol/mg per min) than for the extensor digitorum longus and soleus. Following castration the Vmax for the levator ani undergoes a significant rise which peaks at 3 days.

Relative binding affinities of testosterone, 19-nortestosterone and their 5 alpha-reduced derivatives to the androgen receptor and to other androgen-binding proteins: a suggested role of 5 alpha-reductive steroid metabolism in the dissociation of "myotropic" and "androgenic" activities of 19-nortestosterone

The relative binding affinities of testosterone (T), 19-nortestosterone (N) and their 5 alpha-reduced derivatives: 5 alpha-dihydrotestosterone (DHT) and 5 alpha-dihydro-19-nortestosterone (DHN) to the androgen receptor of the rat seminal vesicle was studied using competition experiments. In cell-free extracts incubated at +10 degrees C for 18 h the relative binding affinities of these steroids (DHT greater than T = DHN = N) proved to be specific for the androgen receptor, in the sense that only prostatic extracts gave a similar result while three other androgen binding proteins (human sex steroid binding globulin, rat epididymal androgen binding protein and an antibody raised against T) exhibited quite different binding specificities. In minced seminal vesicles incubated at 37 degrees C for 1 h the binding affinities showed marked differences (DHT greater than N greater than T greater than or equal to DHN) and similar patterns were observed with both the cytoplasmic and the nu clear receptors. Our findings suggest that (I) the simultaneous presence of a 4-ene double bond and 19-methyl group in T does not favor the tight binding of T to the androgen receptor; therefore, either saturation of this double bond or elimination of the 19-methyl group leads to increased binding and (II) while 5 alpha-reduction of T increases the affinity of this steroid to the receptor, that of N does not influence or rather tends to decrease the binding affinity. The opposite changes observed in the binding affinities of T and N after their 5 alpha-reduction may account for the lower androgenicity of N. On the other hand, the relative myotropic activity in vivo of these steroids is apparently determined by the ratio of their affinities (N/T approximately 3 at 37 degrees C) to the androgen receptor.

Specific cytosol binding of diethylstilbestrol in rat skeletal muscle

Rat skeletal muscle cytosol proteins bound 3H-diethylstilbestrol (3H-DES). More than 90% of this binding was high capacity and low affinity. Serum albumin accounted for roughly 50-60% of the binding, as evidenced by its precipitation with anti-rat albumin IgG. About half of the binding was distinguishable from albumin and other serum proteins by its precipitation in 40% saturated ammonium sulfate. This material sedimented at 4-5S in high-salt sucrose gradients, and resolved into two components (8S and 4-5S) in low-salt. Following incubation at 23-27 degree C for one hour, 2% of the bound 3H-DES in whole cytosol (approximately 2 fmole/Mg cytosol protein) was retained by DNA cellulose, and was eluted with 0.6 M KCl. This small fraction of the total binding was inhibited by estrogens and DES analogues: estradiol-17 beta, DES, dienestrol, and hexestrol were strong inhibitors; isodienestrol, dimethylstilbestrol, estradiol-17 alpha, estrone, tamoxifen, MER-25, CI-628, and nafoxidine were weak inhibitors; dihydrotestosterone, testosterone, and prednisone did not compete. These observations indicate that specific estrogen-binding sites exist in rat skeletal muscle.

Steroid hormone content in the submandibular gland of normal and pregnant rats

Using radioimmunoassay, the levels of steroid hormones were determined in the submandibular gland homogenates from sexually immature, mature male and female and pregnant rats. High progestagen content was established in the whole gland of maturing and mature females and males. The highest level of progestagens was in the last pregnancy trimester. High androgen content was found in maturing and mature males only. Androgens in females and oestrogens in both males and females were present in traces only.

Cytosolic androgen receptor in regenerating rat levator ani muscle

The development of the cytosolic androgen receptor was studied after degeneration and regeneration of the rat levator ani muscle after a crush lesion. Muscle regeneration appears to recapitulate myogenesis in many respects. It therefore provides a model tissue in sufficiently in large quantity for investigating the ontogenesis of the androgen receptor. The receptor in the cytosol of the normal levator ani muscle has binding characteristics similar to those of the cytosolic receptor in other androgen-sensitive tissues. By day 3 after a crush lesion of the levator ani muscle, androgen binding decreased to 25% of control values. This decrease was followed by a 4-5 fold increase in hormone binding, which attained control values by day 7 after crush. Androgen binding remained stable at the control value up to day 60 after crushing. These results were correlated with the morphological development of the regenerating muscle after crushing. It is concluded that there is little, if any, androgen receptor present in the early myoblastic stages of regeneration; rather, synthesis of the receptor may occur after the fusion of myoblasts and during the differentiation of myotubes into cross-striated muscle fibres.

Hormone receptors of the baboon cardiovascular system. Biochemical characterization of myocardial cytoplasmic androgen receptors

Using the synthetic androgen R1881 (17 beta-hydroxy-17alpha-methyl-estra-4, 9, 11-trien-3-one) as probe, we identified cytoplasmic androgen receptors in baboon myocardium. The relative binding affinity of selected steroids for the androgen receptor was R1881, 100%; 5alpha-dihydrotestosterone, 32.6%; testosterone, 29.6%, progesterone, 7.2%; R5020, 1.0%; and estradiol-17beta, 5.8%. The androgen receptor migrated on low ionic strength linear sucrose density gradients as a macromolecule with a sedimentation coefficient of 8.5S. Saturation analysis performed at 2 degrees C (available sites) showed that the androgen receptor content of baboon myocardial cytoplasmic extracts was 5.9 +/- 1.4 fmol/mg protein and that the dissociation constant for R1881 was 1.16 +/- 0.30 nM. These cytoplasmic androgen receptors are indicated to be physiologically functional by previous autoradiographic studies (McGill et al., 1980; McGill and Sheridan, 1981) that showed localization of radioisotope in nuclei of myocardial fibers following injection of baboons with 5 alpha-dihydrotestosterone.

Demonstration and partial characterization of a 7,12-dimethylbenz[alpha]anthracene-binding protein in rat adrenal

Rat adrenal cytosol was found to contain a 7,12-dimethylbenz[a]-anthracene (DMBA)-binding protein which is characterized by a pI of 7.2, a Kd-value of 3 microM and a maximal capacity of about 47 pmol/mg protein. The binding is highly specific for DMBA and is not displaced by 3-methylcholanthrene (MC), benz[a]pyrene (BP) or other polycyclic hydrocarbons. Likewise, various androgens, estrogens or glucocorticoids have no effect on the DMBA binding. It is proposed that the DMBA-binding protein may have a role in the toxic effects of DMBA or DMBA metabolites in adrenal and possibly in other DMBA-sensitive organs as well.

Androgen metabolism in rat skeletal muscle in vitro

Androgen metabolism by the cytosol fraction of rat skeletal muscle was investigated. Testosterone metabolism was low, the main metabolite being 4-androstene-3 alpha,17 beta-diol. In addition, small amounts of 5 alpha-androstane-3 alpha, 17 beta-diol were formed, but no 17 beta-hydroxy-5 alpha-androstane-3-one could be detected. 4-Androstene-3 alpha,17 beta-diol was metabolized only to testosterone in this system of incubation. When 17 beta-hydroxy-5 alpha-androstane-3-one was incubated with muscle cytosol, considerable metabolism to 5 alpha-androstane-3 alpha,17 beta-diol and to 5 alpha-androstane-3 beta,17 beta-diol could be detected. Low 5 alpha-reduction of testosterone and rapid conversion of formed 17 beta-hydroxy-5 alpha-androstane-3-one to 5 alpha-androstane-3 alpha,17 beta-diol and 5 alpha-androstane-3 beta,17 beta-diol gave limited ability of the muscle preparation employed to accumulate 17 beta-hydroxy-5 alpha-androstane-3-one.

Androgen affects cholinergic enzymes in syringeal motor neurons and muscle

We examined the role of testosterone (T) in regulating the weight of the songbird syrinx and the activity of two cholinergic enzymes, choline acetyltransferase (CAT) and acetylcholinesterase (AChE). Castration of adult male zebra finches or neonatal canaries results in a lowering of syringeal weight and CAT and AChE activity. Administration of T for 1-4 weeks restores syringeal weight and AChE to intact levels in male zebra finches. Activity of CAT in muscle is not fully restored. Ovariectomy of female zebra finches and canaries does not affect these syringeal parameters, but T administration to ovariectomized females for 1 month increases syringeal weight and AChE activity. In the zebra finch tracheosyringealis nerve, activity of CAT and AChE is decreased one month after castration. T administration to castrates maintains nerve AChE activity but not CAT. In contrast to changes in the syrinx, tongue muscles do not change in weight or enzyme activity when circulating T levels are altered. Effects of muscle use and disuse were found on syringeal weight and AChE activity, but an androgenic effect also operates in addition. Results suggest that one mechanism for T regulation of singing in passerine birds is through induction of specific enzymatic proteins in androgen target neurons and muscles.

The effect of trenbolone acetate with time on the various responses of protein synthesis of the rat

1. The anabolic agent trenbolone acetate (3-oxo-17beta-hydroxy-4,9,11-oestratriene acetate; TBA) given subcutaneously to female rats increased their growth rate compared with that of the placebo-treated controls. 2. The increased growth rate of the TBA-treated rats was not a consequence of an increased water retention. The TBA-treated rats had a significantly higher (P less than 0.01) total carcass nitrogen content but the total carcass fat content decreased by a non-significant (P greater than 0.05) 8.3%. 3. There was evidence of a time-lag in the response of the fractional synthetic rate of certain individual tissues to TBA. The fractional synthetic rates of the uterus and skeletal muscle mixed tissue proteins were significantly reduced in the TBA-treated rats. 4. The measured reduction in fractional synthetic rates was concluded to reflect true changes in the synthetic rate rather than a result of an alteration in the specific activity of the tyrosine pool used for protein synthesis.

Evidence for nuclear and DNA binding forms of the receptor-glucocorticoid complex from hepatoma tissue culture cells

Binding to DNA associated with cellulose has been used to investigate the receptor-glucocorticoid complex isolated from a line of rat hepatoma tissue culture cells. The amount of activated complex that bound to DNA was approximately half that which bound to nuclei. Additional results suggest the existence of two forms of the activated glucocorticoid receptor-steroid complex in about equal amounts: one form binds only to nuclei and the other binds to DNA and nuclei. The two forms also differ in their stability, with the DNA/nuclei binging form being relatively labile. The binding of either form to the appropriate acceptor is reduced by cytosol inhibitors by the same mechanism.

Male pseudohermaphroditism due to steroid 5-alpha-reductase deficiency

A new inherited form of male pseudohermaphroditism has been investigated in a pedigree of 24 families with 38 affected males. At birth, the affected males (46 XY) have a clitoral-like phallus, bifid scrotum and urogenital sinus. The testes are in the inguinal canals or labial-scrotal folds. The Wolffian structures are normally differentiated; there are no Mullerian structures. At puberty a muscular male habitus develops with growth of the phallus and scrotum, voice change and no gynecomastia. The subjects have erections, ejaculations and a libido directed towards females. They have decreased body hair, a scant to absent beard, no temporal hair line recession and a small prostate. Testicular biopsy reveals a normal testis. The mean plasma T levels in affected adults are significantly higher, and the mean plasma DHT levels are significantly lower when compared to those in normal subjects. The plasma T:DHT ratios range from 35 to 84 compared to 8 to 16 in normal subjects. After the administration of hCG, the T:DHT ratios in affected male children range from 74 to 162 compared to 3 to 26 in the control subjects. In affected adults, mean plasma LH and FSH levels are significantly higher than in normal subjects. In the affected subjects, the metabolic clearance rates of T and DHT are normal, but the conversion ratio of T to DHT is less than 1 per cent. The endogenous mean urinary E:A and E-OH:A-OH ratios, and the urinary E:A and E-OH:A-OH ratios after the infusion of radioactive T are significantly higher than in normal males. Inheritance is autosomal recessive with some sibling sisters showing the same biochemical defect, and obligate carrier parents showing an intermediate defect. These data support our thesis that the defect in these male pseudohermaphrodites is secondary to decreased steroid delta 4-5 alpha-reductase activity. The affected subjects provide a clinical model for delineating the roles of T and DHT in sexual differentiation and development. This entity also demonstrates an inherited disorder of steroid metabolism in which the basic enzyme deficiency resides in the target tissues.

Determination of rat muscles androgen-receptor complexes with methyltrienolone

In the present study, "in vitro" evidences are shown for the existence of a highly active 3alpha-hydroxysteroid dehydrogenase in the crude cytosol of rat muscle homogenates; the use of 5alpha-dihydrotestosterone (DHT) is therefore compromised in receptor binding measurements because of its extensive metabolism. The synthetic anabolic androgen, methyltrienolone (MT) palliates this disadvantage of DHT. Both steroids, as well as testosterone, appear to be bound to an 8 - 8.5 S androgen receptor on sucrose density gradient. The androgen receptor in the vastus and the levator ani bulbocavernosus complex (LA/BC) shows similar association constants, but the number of binding sites in LA/BC is about 5 times higher than in vastus. Otherwise, the total number of muscle androgen receptors seems to be invariant in adult and aged rats. The binding to these macromolecules can thus be measured "in vitro" provided specific and sensitive methods are utilized.