Rat Androgen Research Articles

The evolutionary tangle of aging, sex, and reproduction and an experimental approach to its molecular dissection.

Exchange of genetic materials by two individual members of the same species is considered to be the origin of primitive sex. During evolution, this primitive form of molecular sex has been transformed into a complex biological function involving specialized sexual structures and multiple hormonal interactions. Development and maintenance of these reproductive structures are also dependent on hormones and hormone receptors. Furthermore, reproductive specialization in higher forms of life has led to customized species-specific rates of aging and life-span potentials that are commensurate with the reproductive needs of the particular type of organism. Because of this reproductive imposition on aging of the organism, temporal regulation of the hormone response is a significant component of the genetics of aging. We have observed a marked age-dependent alteration in the hepatic expression of the rat androgen receptor (rAR) gene. Among the large number of transcription factors that control the rAR gene, at least three appear to participate in its age-dependent regulation. Two of these are positively acting and yet/to be characterized transcription factors, while the third is a negative regulator the nuclear factor kappa B (NF-kappa B). NF-kappa B is the major trans-regulator for genes involved in the immune response, inflammation, and oxidative stress. Involvement of NF-kB in the modulation of both oxidative stress and sex function provides the first example of a common molecular link between sex and aging.

The Development of Casodex™ (Bicalutamide): Preclinical Studies

Casodex (bicalutamide, Zeneca Limited) was developed for the treatment of prostate cancer from a series of nonsteroidal compounds related to flutamide. Casodex is a selective antiandrogen that binds to rat, dog and human prostate androgen receptors, and has approximately a 4-fold higher affinity for the rat androgen receptor than hydroxyflutamide, the active metabolite of flutamide. Casodex also binds to androgen receptors found in the LNCaP human prostate tumour and the Shionogi S115 mouse mammary tumour cell line, as well as androgen receptors transfected into CV-1 and HeLa cells. In all cases, Casodex behaves as a 'pure' antiandrogen and inhibits gene expression and cell growth stimulated by androgens. Studies in vivo show that Casodex is a potent antiandrogen in the rat. In contrast to flutamide, which produces dose-related, marked increases in serum luteinising hormone (LH) and testosterone, Casodex has little effect on serum LH and testosterone; that is, it is peripherally selective. The peripheral selectivity of Casodex has now been shown to be due to poor penetration across the blood-brain barrier. In dogs, Casodex has exquisite potency and causes dose-related atrophy of the prostate gland and epididymis; with an oral ED50 of 0.1 mg/kg, it is about 50 times as potent as flutamide in this species. Casodex is also peripherally selective in the dog. In addition, magnetic resonance imaging studies have shown that Casodex is a potent antiandrogen in the monkey. Casodex, at a daily oral dose of 25 mg/kg effected a highly significant reduction in the growth of Dunning R3327H transplantable rat prostate tumours that was equivalent to that achieved by either surgical or medical castration with the LH-releasing hormone agonist Zoladex (goserelin). In a comparative study, flutamide was shown to be both less potent and less active than Casodex. In these preclinical studies, Casodex was well tolerated. The preclinical properties of Casodex give it advantages, with respect to potency, tolerability and the maintenance of effective antiandrogen serum concentrations, over other available antiandrogens. Moreover, it has a half-life that is compatible with once-daily administration.

Immunohistochemically demonstrated androgen receptor expression in the rat prostate during carcinogenesis induced by 3,2′-dimethyl-4-aminobiphenyl with or without testosterone

A polyclonal antibody against rat androgen receptor was used to investigate its expression during 3,2′-dimethyl-4-aminobiphenyl (DMAB)-induced prostate carcinogenesis in the rat. Fixation in cold-acetone provided better observation of specific nuclear staining than 10% buffered formalin. Normal epithelial cells and atypical hyperplasias in all lobes were positive. Ventral prostate carcinomas were also strongly positive for androgen receptor (AR) but most invasive carcinomas arising from the dorsolateral prostate and seminal vesicles, which were induced by DMAB plus testosterone propionate, were AR negative. Atypical hyperplasias of those organs were all positive. These findings suggest that ventral carcinomas are androgen dependent but carcinomas in other lobes become independent during progression.

Effects of Submaxillariectomy on Ovarian Androgen and Estrogen Production in Adult Female Rats

Submaxillariectomy causes an increase in uterine weight in adult female rats. This increase is due to the elevation of the plasma 17β-estradiol (E2) level which is brought on by enhancement of ovarian E2 production. Furthermore, enhancement of ovarian E2 production is due to the enhancement of testosterone and androstenedione production which are the precursors of ovarian E2. However, submaxillariectomy did not affect ovarian progesterone and 17α-hydroxyprogesterone levels. These findings suggest that the submaxillary gland may inhibit the production of ovarian E2 mainly because of the inhibition of ovarian androgen production. Thus the submaxillary gland may play a physiological role in female reproductive systems caused by the change in ovarian steroidogenesis.

Search for androgen response elements in the proximal promoter of the canine prostate arginine esterase gene.

We have demonstrated the binding of the recombinant DNA binding domain of the rat androgen receptor to a DNA sequence of the canine prostate arginine esterase gene and have determined the functional significance of this sequence in transient transfection experiments. One of the binding sites was localized to a region (-172 to -148 bp) containing the sequence AGGACAACAGGTGTT that has 73% homology with the prostate-specific antigen (PSA) androgen response element (ARE) found at a similar position in the PSA promoter. Competition experiments showed that the androgen receptor had an approximately 100-fold more affinity for the PSA ARE than for the arginine sequence at -172 to -148. Transient cotransfection of 5'-deletion mutants of the arginine esterase promoter and 5'-flanking sequences driving the activity of the reporter gene along with the rat androgen receptor expression vector yielded only negligible inductions of chloramphenicol acetyl transferase (CAT) activity when dihydrotestosterone (DHT) was added to the culture medium. The introduction of one to four repeats of the -172 to -148 sequence of the arginine esterase gene upstream of the basal promoter of the mouse p12 gene in p12.108 also resulted in a minimal induction of CAT activity compared with a 10-fold induction of PSA AREs under similar conditions. These results suggest that the regulation of the canine arginine esterase gene by androgens is most probably achieved by mechanisms that differ from the ones prevailing with the human PSA and kallikrein-2 (hKLK2) genes.

Regulation of androgen action by receptor gene inhibition.

Regulated functions of hormonal agents play a critical role in health and disease. Target cell responsiveness to a hormonal signal is a product of both cellular concentrations of the hormone ligand and the corresponding receptor protein. The major thrust of the drug design for treatment of endocrine-related problems, so far, has been directed to ligand derivatives. In certain cases, receptor regulation through antigene technology has much to offer with improvements in both target cell and hormonal specificity. Three different antigene approaches are currently being explored. The first approach is to inhibit the expression of the receptor gene by disrupting the DNA protein interaction at critical cis-elements by short triple helix-forming oligonucleotides. The second approach is to sequester and inactivate the receptor mRNA by the antisense mRNA produced in the target tissue directed by a heterologous tissue-specific promoter. The third approach is the tissue-specific expression of a catalytic ribozyme that binds to the specific receptor mRNA and selectively degrades it before its translation into the protein. In this study, we have characterized the promoter of the rat androgen receptor, and by progressive deletion from its 5' end have identified two critical cis-regulatory elements, one at the -960 to -940 region and the other at the -554 to -574 positions. The former is an activator while the latter is an inhibitor domain. The inhibitory domain is the binding site for the nuclear factor kappa B (NF-kappa B) and more specifically, the p50/p50 homodimer of this transcription factor family. We have also provided correlative data to show that under normal physiological conditions, the NF-kappa B functions as an antiandrogen during the age-dependent desensitization of the liver. In addition to the naturally functioning antiandrogenic influence of NF-kappa B, we have designed an artificial antiandrogenic agent, a triplex-forming oligonucleotide (TFO) directed to the -960/-940 activator domain of the rat androgen receptor gene promoter. This oligonucleotide at a TFO-to-promoter ratio of 500 is able to cause about 60% inhibition of rAR promoter function in transfected COS-1 cells. These results clearly demonstrate the feasibility of the antigene approach for effective inhibition of steroid hormone action.

Nuclear Factor κB Functions as a Negative Regulator for the Rat Androgen Receptor Gene and NF-κB Activity Increases during the Age-dependent Desensitization of the Liver

Transcriptional regulation of the steroid hormone receptor genes plays a central role in temporal changes of target cell sensitivity during development, maturation, and aging. Sequence-specific DNA-protein interactions mediate these regulatory functions. Progressive 5' deletion of the rat androgen receptor (rAR) gene immediately beyond the -572 base pair (bp) region causes a marked increase in its promoter activity. DNase I footprinting with nuclear proteins revealed a protected area encompassing -574- to -554-bp positions that begins with a perfectly palindromic nuclear factor kappa B (NF-kappa B) motif. Electrophoretic mobility shift analyses (EMSA) showed that the decameric rAR NF-kappa B site at positions -574 to -565 cross-competes with the authentic kappa immunoglobulin light chain enhancer for specific protein binding. Supershift with specific antibodies to NF-kappa B subunits confirmed that the two retarded bands observed in the EMSA with the labeled rAR probe are due to p50/p65 and p50/p50 dimers of the NF-kappa B/Rel proteins. Fragments of rAR promoter with either deletion or point mutation of the NF-kappa B site are found to be about 2- to 3-fold more effective as compared to the wild type control in driving a heterologous reporter gene in cellulo. Thus, unlike most other known cases, NF-kappa B acts as a negative regulator for the rAR gene. The physiological relevance of this repressor function is evident from a 10-fold increase in the p50/p50 form of the NF-kappa B activity in the liver of aged rats exhibiting hepatic androgen desensitization. The newly identified repressor element is a rare example of a naturally occurring perfect palindromic binding motif for the NF-kappa B/Rel family of transcription factors. This repressor factor and the positively acting age-dependent factor, ADF, described earlier (Supakar, P. C., Song, C. S., Jung, M. H., Slomczynska, M. A., Kim, J.-M., Vellanoweth, R. L., Chatterjee, B. & Roy, A. K. (1993) J. Biol. Chem. 268, 26400-26408) function to coordinate the tissue-specific down-regulation of the rAR gene during aging.

Presence of nuclear androgen receptor-like immunoreactivity in neurokinin B-containing neurons of the hypothalamic arcuate nucleus of the adult male rat

Dual label immunofluorescence was used in the brain of normal, non colchicine-treated, adult male rats in order to characterize the neurons possessing the nuclear androgen receptor in the hypothalamic arcuate nucleus. The affinity purified PG21 rabbit serum to the rat androgen receptor (AR) was used in conjunction with a polyclonal guinea pig antiserum to peptide 2, a sequence within the precursor to neurokinin B (NKB). All NKB-containing neurons were also immunoreactive for the AR, and made up a large proportion (about 60%) of the arcuate cells with detectable and specific AR immunoreactivity.

The androgen receptor mRNA is up-regulated by testosterone in both the harderian gland and thumb pad of the frog, Rana esculenta

α32P-labelled cDNA probe from plasmid containing rat androgen receptor (rAR) has been tested in hybridization experiments using RNAs from the Harderian gland and thumb pad of the edible frog, Rana esculenta. Northern blot analysis has shown a high degree of homology between the rAR cDNA and the frog androgen receptor mRNA (fAR mRNA); this has been supported by both the hybridization conditions (high stringency) and the molecular size of fAR mRNA which is quite similar to those described in mammals (9.4 kb). The role of androgens has been further investigated with respect to the kinetics of expression of fAR mRNA in in vivo experiments. In both the Harderian gland and thumb pad, testosterone has increased the levels of fAR mRNA as compared with the untreated groups. The use of cyproterone acetate (CPA) in combination with testosterone has resulted in a loss of the increase in fAR mRNA as compared to testosterone-treated groups, while CPA alone has resembled the control group. In primary cultures of frog Harderian gland and thumb pad cells, the steady-state levels of fAR mRNA have been increased in the cells exposed to testosterone as compared to those not exposed. These findings confirm that, in these androgen target tissues, testosterone exerts an up-regulation on its own receptors, increasing the accumulation of fAR mRNA in the same way as oestrogens up-regulate the expression of their own receptors in Xenopus liver and oviduct cells.

Synergistic effects of estrogen with androgen on the prostate--effects of estrogen on the prostate of androgen-administered rats and 5-alpha-reductase activity.

To clarify the effects of estrogen on the prostate of androgen-treated rats, we administered estradiol (E2; 0.01 mg/day) to testosterone (T; 1 mg/day)-treated Wistar rats under various conditions. There were three variable factors: the age of the rat, the untreated period after castration, and the presence of testes. Under all conditions, E2 stimulated the growth of the prostate in T-treated rats compared with growth in rats in treated with T only. To analyze the mechanism underlying this enhancement of prostate growth by estrogen, we measured 5-alpha-reductase activity and calculated its kinetic parameters, i.e., both Vmax and Km. The Vmax of the nuclear fraction was higher in E2-administered T-treated rats than in T only-treated rats. In contrast, the Vmax of the microsomal fraction was lower in E2-administered rats. Km values in the two groups showed no significant differences. Elevation of the nuclear fraction of 5-alpha-reductase activity could explain the synergistic effects of estrogen on the prostate growth of androgen-treated rats.

Both Sertoli and peritubular cells respond to androgens with increased expression of an androgen response element reporter.

To explore the ability of androgens to affect gene expression in Sertoli and peritubular cells in vitro, constitutively expressed pSV2-Luc and a regulated reporter containing an androgen response element (MMTV-Luc) were transiently transfected into these cells. Reporter expression was markedly affected by cell density and maturational age. Mibolerone-stimulated MMTV-Luc expression increased in Sertoli cells with animal age between 15 and 25 days, consistent with the developmental increase in androgen receptor concentration, but was not markedly age-dependent in peritubular cells. The antiandrogen hydroxyflutamide inhibited stimulation of MMTV-Luc expression by 1 and 10 nM testosterone in both Sertoli and peritubular cells, consistent with an androgen receptor-mediated event. In contrast, dexamethasone at 1 and 10 nM elicited no effect in Sertoli cells, but stimulated MMTV-Luc expression in peritubular cells. In this study, the androgen receptor/glucocorticoid receptor ratio was 2.4 and 0.06 in Sertoli and peritubular cells, respectively. Cotransfection of Sertoli and peritubular cells with a plasmid expressing the rat androgen receptor further increased the androgen-stimulated expression of MMTV-Luc. These data demonstrate the functionality of the androgen receptors in both Sertoli and peritubular cells in culture. Receptor expression appears to be a limiting factor in the response. The data are consistent with potential roles for both Sertoli and peritubular cells in androgen-mediated transcriptional events in the testis.

Structure-function relationships of rat androgen--binding protein/human sex-hormone binding globulin: the effect of mutagenesis on steroid-binding parameters.

Androgen-binding protein (ABP) and plasma sex hormone-binding globulin (SHBG) are encoded by the same gene and have the identical amino acid sequence within a species. Mammalian ABPs and SHBGs bind sex steroids with high affinity, but some binding properties differ among species. Human SHBG has a higher affinity for steroids and forms a more stable 5 alpha-dihydrotestosterone (DHT) complex (t1/2 = 40 min) than rat epididymal ABP (t1/2 = 5 min) at 0 C. In this study it was found that recombinant wild-type rat ABP/SHBG bound DHT and estradiol with nearly the same affinities as human SHBG, rather than the affinities of rat epididymal ABP. This finding is reminiscent of our previously published data demonstrating that ABP secreted by cultured Sertoli cells had a higher affinity for DHT than did epididymal ABP. Recombinant wild-type ABP had DHT dissociation properties similar to those of rat epididymal ABP. The differences in binding properties of epididymal ABP and recombinant ABP could in part be caused by intrinsic differences in the properties of the proteins due to posttranslational modifications or allelic variations in sequence. To aid in identification of the steroid-binding domain of ABP and SHBG, we developed recombinant rat ABP/SHBG chimeras containing human sequences in and flanking the putative steroid-binding region (residues 134-150). Four regions were mutated: 1) residues 129-132; 2) residues 133-138; 3) residues 148-155; and 4) 165-169; residues between these regions are identical in rat and human ABP/SHBG. Wild-type (ABPwt) and mutant proteins were expressed in COS cells, and their steroid-binding properties were determined. Conversion of rat amino acid residues 133-169 (ABP2,3,4) to human ABP/SHBG sequence resulted in a 2-fold increase in affinity for estradiol compared to ABPwt. Another mutant ABP2,3,4; Leu 137, which contained the rat Leu137 residue, had a 5-fold increase in estradiol affinity. Conversion of residues 129-132 to human sequence in ABP2,3,4 to form ABP1,2,3,4 resulted in a dramatic decrease in estradiol affinity. Conversion of each region separately also resulted in some changes in steroid-binding properties. The largest change was observed with ABP1, which had a 3-fold reduction in estradiol affinity compared to ABPwt. There was a 14-fold difference in estradiol affinity between ABP1 and ABP2,3,4; Leu 137. Alterations of some individual amino acid residues in region 2, which is the least conserved region between rat and human, caused subtle or major changes in the estradiol-binding properties; none affected DHT binding.(ABSTRACT TRUNCATED AT 400 WORDS)

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) overexpressing 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 ∼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 competed by addition of unlabeled excess of GRE but not of unspecific oligonucleotides, confirming sequence-specific binding of the R1881-induced protein-GRE complex.

Analysis of androgen receptor-DNA interactions with receptor proteins produced in insect cells

Wild-type rat androgen receptor and four of its deletion mutants were produced in insect cells using the baculovirus expression system. Inclusion of androgen, but not estrogen, progesterone, or glucocorticoid, in culture medium increased the yield of soluble androgen receptors, although the majority of receptors still remained in the insoluble form (Xie, Y.-B., Sui, Y.-P., Shan, L.-X., Palvimo, J. J., Phillips, D. M., and Jänne, O. A. (1992) J. Biol. Chem. 267, 4939-4948). The wild-type receptor interacted with an androgen response element (ARE) with a 2-6-fold higher affinity (KD = 0.5 nM) than mutants with deletions outside the DNA-binding domain (delta 40-147, delta 38-296, delta 46-408, and delta 788-902 mutants), suggesting that sequences flanking the DNA-binding region influence the stability of receptor-DNA complexes. Changes in spacing (n = 3) between the two ARE half-sites by a single nucleotide (n - 1, n + 1) or by 10 bases (n + 10) abolished the full-length receptor's ability to form stable complexes with DNA. Binding to AREs with altered spacing could not be restored by antisera against the N-terminal domain of the receptor that stabilize androgen receptor-DNA interactions with many naturally occurring strong and weak AREs. Methylation interference and 1,10-phenanthroline copper footprinting analyses revealed that the receptor binds to DNA as a dimer. Dimer formation was demonstrated directly by mixing full-length and delta 46-408 mutant receptors, which resulted in the formation of heterodimeric receptor-DNA complexes. The half-time of dissociation of the wild-type receptor from a consensus ARE sequence was about 3 min at 22 degrees C. Collectively, androgen receptor binds to DNA with properties similar to, but not identical with, those of glucocorticoid receptor, indicating that regions outside the DNA-binding domain are important to ensure androgen specificity of transcriptional regulation.

Suppression of sodium channel function in differentiating C2 muscle cells stably overexpressing rat androgen receptors

Differentiation of skeletal muscle and the formation of the neuromuscular junction are regulated by steroid hormones. The effects of androgens on ion channel proteins central to neuromuscular signalling have been investigated in differentiating mouse muscle C2 cells and in C2 cells that stably overexpress the rat androgen receptor (AR) cDNA. Neither the expression nor function of ACh receptors was regulated by androgenic actions in these cells. However, voltage-dependent sodium (Na) current density was decreased by androgen treatment of C2 cells and was abolished, even in the absence of androgens, in C2 cells that overexpress the AR. The decrease in functional Na current was not accompanied by concomitant decreases in Na channel mRNA, suggesting that AR influence posttranscriptional processing of Na channels in differentiating C2 cells.

Effects of antiandrogen TZP-4238 on the prostatic androgen receptor and prostatic androgen in rat

TZP-4238, a new steroidal antiandrogen, is an orally active drug in rats and dogs. The effects of TZP-4238 on the androgen receptor and androgen content were examined in comparison with other antiandrogens in rats. The prostate DHT levels decreased markedly within 4-8 hr after a single oral administration of TZP-4238 8mg/kg. The prostatic testosterone concentrations fell below the detection limit (5pg/g of tissue) at 4-12 hr after the initiation of treatment. The plasma testosterone level also fell to 60% of the control level after 4-8 hr and then returned to the normal range. Eight percent of DHT present in normal prostatic tissue was located in the nuclear fraction. TZP-4238 reduced the concentration of DHT in nuclei to 50% of the normal level. The concentration of the plasma drug which induced a 50% decrease in the prostatic DHT, the IC50, was about 10ng/ml, while the IC50 value for plasma testosterone was 30-50ng/ml. After oral administration of 15-OH TZP-4238, the main metabolite, the level of plasma testosterone was significantly elevated above the control level. The androgen receptor level was markedly reduced at 24 hr following castration and returned to the normal range within 5 hr of a single injection of testosterone. TZP-4238 reduced the nuclear androgen receptor level to 60% at 24 hr after a single oral dose and then, the receptor content returned to its original level. Both 15-OH TZP-4238 and cyproterone acetate also reduced the androgen receptor and DHT contents to 50%. A series of in vivo studies demonstrated that TZP-4238 inhibited the uptake of testosterone and the decrease of DHT and testosterone, and decreased the nuclear androgen receptor in the rat prostate.

Non-steroidal antiandrogens: Synthesis and biological profile of high-affinity ligands for the androgen receptor

New N-substituted arylthiohydantoin antiandrogens were synthesized. These compounds presented exceptionally high relative binding affinities (RBAs) for the rat androgen receptor (AR): up to 3 times that of testosterone (T) and 100 times the RBAs of non-steroidal antiandrogens such as flutamide, Casodex and Anandron. Furthermore, unlike available markers for AR, they were totally devoid of any binding to the other steroid receptors. RU 59063, the molecule with the highest RBA, was tritiated. When it was compared to [ 3H]T for the assay of rat, mouse, hamster and AR, it gave rise to the same number of binding sites but its K a (6×10 9 M −1) for rat and human AR were, respectively 3 and 8 times higher than that of T. Moreover RU 59063, unlike T, was devoid of any specific binding to human plasma. In vivo, these compounds displayed antiandrogenic activity while being devoid of any agonistic effect. Thus, RU 56187, given orally in castrated male animals, prevented in a dose-dependent manner the effects of 3 mg/kg testosterone propionate (TP) on mouse renal ornithine decarboxylase (acute test) and of 0.5 mg/kg TP on rat prostate weight (chronic test). In these two models, its ED 50 was 0.6 and 1 mg/kg, respectively. In the intact rat, when given alone, it inhibited dose-dependently the effect of endogenous androgens on the seminal vesicles (ED 50 ≈ 1 mg/kg) and prostate (ED 50 ≈ 3 mg/kg) weights. These results suggest that these new compounds may be useful as specific markers for the androgen receptor as well as for the treatment of androgen-dependent diseases or disorders such as prostate cancer, acne, hirsutism and male pattern baldness.

Effect of antiandrogen treatment on chemical hepatocarcinogenesis in rats

We studied the effect of antiandrogen treatment on the Solt-Farber model of hepatocarcinogenesis in male Sprague-Dawley rats. The size and number of the liver tumors were reduced by various antiandrogen treatments (orchiectomy, an LH-RH analog, and chlormadinone acetate). In addition, the proportion of poorly differentiated carcinomas was decreased by the antiandrogen treatment, while that of well-differentiated trabecular or glandular carcinomas was increased. The bromodeoxyuridine labeling index of the tumor cells was significantly decreased after the antiandrogen treatment. The expression of rat androgen receptor mRNA in carcinoma tissue was increased when compared to control liver tissue, and was decreased after the antiandrogen treatment. Orchiectomy had the greatest inhibitory effect on carcinoma, although the effect of chemical orchiectomy using an LH-RH analog was almost similar to that of orchiectomy. These results suggest that the clinical application of antiandrogen therapy for human hepatocellular carcinoma might be possible in the future.

Suppression of sodium channel function in differentiating C2 muscle cells stably overexpressing rat androgen receptors

Suppression of sodium channel function in differentiating C2 muscle cells stably overexpressing rat androgen receptors

The influences of androgen on sociosexual behavior: A comparison between the spontaneously hypertensive (SHR) and the Wistar-Kyoto rat (WKY)

Differences in androgen-dependent forms of behavior and plasma testosterone levels in the spontaneously hypertensive rat (SHR) and its normotensive counterpart the Wistar-Kyoto rat (WKY) are described here. Copulatory behavior (solitary test to avoid influence of experience) and certain androgen-dependent elements of sociosexual orientation were significantly attenuated in the SHR compared to the WKY male rat. After castration, the differences in sociosexual orientation were no longer apparent. In contrast, differences in other behavioral elements, such as locomotion, were unchanged after castration. Plasma testosterone levels were significantly higher in the SHR than in the WKY male rats. Taken together, the behavioral and hormonal data suggest a decreased central nervous responsiveness to androgens in the SHR rats. This could lead to reduced androgen-dependent behavior, and possibly also to a decreased testosterone feedback control.